Most programs rank their applicants like instructors grade tests. GRE scores may count for 30% of the test, GPA, 20%, writing statement 30%, and rest 20%.
Your undergraduate GPA is "okay," and you have social science training (b.a. in political science), but even with the fullbright (which is a MAJOR plus) they will have serious questions as to why you didnt take a stats and methods in undergrad (some programs require applicants to have it). You can apply to an MA program in Demography, but they'll likely have the same questions and/or offer little funding. You could go to a lower ranked and/or non-american school, but moving up the ranks (which it appears you want to do) may prove very very rough.
You might want to look at a top 25 master's in public policy, social policy, public affairs programs, or something social sciency. Since these programs draw students from a variety of fields, they wont expect you to have any methods or stats training and if they do, will be more flexible. While in the program, you'll likely take a graduate level statistics course (do well in it), and if you can, take it in sociology. Try to use an elective to take a methods course in sociology and/or a course taught by someone who has a background in sociology.
After you complete the program (providing you do well which I'm sure you'll do), you'll be VERY attractive and fundable to top tier programs.
That's my two cents....