Those are all good signs! An hour and a half interview? Wow. I wonder how many applicants they are interviewing. My friend had a phone interview with Syracuse for the SLP program and she said it was a very relaxed interview, they just wanted to get a feel for her personality and ask why their program/why Syracuse? You'll do great, don't worry!
You must have a car in Houston unless you live on campus. But getting around to places like the grocery store and restaurants would be difficult. With the weather, you'd want to have a car.
Bikers are not treated well there. There aren't even bike lanes and it's very unusual to see a bike on the road at all. I visited my family last fall and tried to bike about 2 miles to a smoothie place and about died from the drivers and the heat. Austin is home of Lance, so it's definitely a more bike friendly city.
You must have a car. I wouldn't live around UH since it's not in the greatest area. I always felt safe on campus, but I wouldn't want to live in some of the apartments right near campus. Houston is a cheap city, with cheap housing and cheap gas. The best thing about Houston: the food. Man do I miss that food. People are friendly. Cons: Traffic sucks and so does the humidity.