That is not an easy question to answer. Tuition at University of Houston is a little less than at Texas A&M and UT. However, you can find a safe, decent place to live for dirt cheap in College Station. That same amount of money in Houston would buy you a crack house. Not to mention the cost of auto. insurance is MUCH cheaper in College Station than Houston (could be as much as $100/month difference).
Unless the tuition at U of H is drastically lower, A&M would be a better choice, with a much wider variety of graduate level science programs as well, as there is both a medical school and a vet school in town.
Other than A&M, obviously the state schools are going to be cheaper than the privates. As another poster mentioned, A&M, UT, U of UH, Sam Houston, SFA, Texas State (formerly SW Texas). Of course there is always the smaller branches of the A&M and UT systems: A&M at Galveston, Commerce, Kingsville, etc.; and UT San Antonio, El Paso, etc. I am not sure how much their tuition varies from the "flagship campuses." They may be lacking in graduate level programs as well.
-Scott, MS3
Texas A&M class of '02!