Caesar

This is probably a bit late for you, but I had no idea that TAMU even had a separate biostat program in the School of Public Health.  I went through the course registration portal and didn't even see any of their supposed courses being offered over the past few semesters.  However, if you're interested in biostats and TAMU then look no further than the TAMU Department of Statistics.  It's one of the largest programs in the country and has people working and doing research in biostat areas ranging from statistical genetics, agriculture, nutrition and toxicology, and oncology (I believe that they have close ties with M.D. Anderson in Houston which is a world leader in cancer research and treatment).

If you are applying for a PhD program (and particularly if you are interested in academia), the reputation of your dissertation adviser is far more important than the reputation of the program where you did your PhD. Thus, I always tell students not to obsess over rankings, because you would be much better off attending a lower-ranked school and working with a star adviser than attending a higher-ranked school and working with a mediocre adviser. And you also have to consider whether or not a department is strong in the areas in which you are interested. To give a couple specific examples, Michigan's biostat program is a fantastic option if you are interested in genetics, but it's not such a great option for most other areas. Likewise Harvard's stat department is small, but it's definitely the best in the world for missing data and a couple other areas. But it would be a mistake to attend Harvard's stat department unless you are interested in one of the research areas where they are strong.
 
That said, it can be advantageous to attend a higher-ranked department, particularly if you're not sure about your research interests when you start grad school (which in my experience is true of a high percentage of students). Typically the higher-ranked departments tend to have strong faculty in a wide variety of research areas. They also tend to be better-funded, so there is less of a concern about having your funding run out after a couple years. Nevertheless it would be a mistake to choose a PhD program purely based on rankings given that there isn't a huge difference between many of the top programs. My advice would be to carefully examine the research interests of the faculty at each school. It's also worth considering funding, quality of life, and things like that. Rankings would be very low on the list of things that I would consider.
 
Having said all that, if you want my feedback on the rankings that people have proposed earlier, I would put UNC in the top tier for biostatistics. Maybe Michigan as well, although they are hard to rank due to being so heavily focused on genetics. But most people say that UW/Harvard/Hopkins/UNC represent the top tier of biostatistics and sometimes Michigan depending on who you talk to. All of the four aforementioned schools have large departments with diverse faculty research interests so practically any student should be able to find a good adviser at any of those schools. After that, I would say that the research interests of the faculty and availability of funding should be more important than rankings, because many of the remaining departments are strong in a couple areas but very weak in other areas.
 
As for statistics, I'm less familiar with the gossip about the quality of the various statistics programs. That said, even among the top-ranked schools, one should consider the research interests of the faculty and how they align with your interests. Some departments have the reputation of being more theoretial (e.g. Berkeley, Chicago) whereas others are more applied (e.g. Stanford, CMU), for instance. But I'm basing this largely on gossip that I heard years ago, so take it for what it's worth. I recommend that you carefully research the faculty research interests of each department you are considering.

I think everyone on this thread is greatly overlooking the importance of recommendation letters. Strong recommendations can cover a multitude of sins whereas lukewarm ones can sink otherwise very promising candidates. I might go so far as to say that they are the single most important part of an application. The only other thing that comes close is grades in advanced math classes, but even that is hard to evaluate at "less prestigious" schools. For applicants with an MS or non-traditional applicants, evidence of research excellence (i.e. publications in good journals) also helps a lot, but it is very rare for someone coming straight out of college to have much of a paper trail in this area.
 
For the record, I would strongly disagree with the claim that undergraduate prestige "matters a lot." Sure, it matters some. If you have a 4.0 at Harvard, you are probably going to be accepted. But I would say that the majority of the students admitted to my department in recent years have not been Ivy League grads but rather students who attended solid state schools and did very well. (And my department is usually considered to be one of the best.) And it's a sample size of 1, but I attended an extreme "no name" undergraduate school and I was still admitted to every graduate program to which I applied. The main difference is that if adcoms aren't familiar with the rigor of the courses at your school, they will rely more heavily on recommendation letters. If a recommender says, "Student X took my proof-based advanced calculus course and got the highest grade of anyone in 10 years," you will be fine. But if you get three tepid recommendations, that may not be good enough.
 
As for undergraduate GPA's, a low undergraduate GPA will not sink you, although the burden of proof will be on you to show that it is not an accurate reflection of your true ability. As I mentioned on another thread, my department recently admitted a student whose undergraduate transcript was almost entirely C's, D's and F's (mostly D's and F's their first two years). But this particular student enrolled in an MS program and got three recommenders saying that they were one of the top MS students in years. They also wrote a publishable paper while in this program. So it is definitely possible to be admitted to a top-ranked department despite a spotty undergraduate record, but you will have your work cut out for you. My advice would be to have a candid talk with your potential recommenders about how strong they are willing to recommend you. If you are in a top-10 department and you can get three recommenders who say that you are strong enough to be in their PhD program, that could carry you quite a ways. And if either of your research projects could result in publishable papers in a good methodology journal, be sure to find a recommender who will say that as well. As cyberwulf correctly noted, your MS GPA probably won't help you that much since usually the curve in these programs is very generous. (If you took some form of advanced calculus/real analysis course where the curve was not inflated in either of your MS programs, try to find a recommender who will say that.)
 
One way or another it's going to be a crap shoot. Your best advice is to apply very broadly. It's unclear to me whether you really cannot stay in your current program or if you just don't want to, but if you are serious about getting a PhD, you should try to make sure you have some kind of backup option. It's really hard to predict what will happen to you. Good luck.

I couldn't disagree more completely with you. Applicants are PAYING MONEY to have their application managed. This means more than just an evaluation by the admissions committee; it should also include communicating to students the status of their application on request. Of course, some anxious students probably email excessively, but this is apparently not the case for the OP or apparently many people on this board. 
 
This attitude of "professors are too busy to deal with graduate students (or prospective students)" really bugs me. If a faculty member is too busy to deal with the responsibilities of admissions, they shouldn't agree to be involved. If all faculty members/administrators are too busy or unwilling to put in the effort, then maybe the department shouldn't be running a graduate program in the first place or at the very least should find some people willing to manage it better.