There's just not a lot of info on the dorms yet, so that's probably why no one has talked about it. Although, I know that personally I need at least my own room, so despite the cheap price (I think it's less than $300/ mo), the dorms are not for me.
You can find out more info about the university dorms here:
http://www2.utmb.edu/housing/
As for the UTMB frats, they are not typically like the frats you might picture. There was some weirdo on the waitlist thread who was dogging UTMB and the medical frats (but yet won't drop his acceptance here so that WE don't have to deal with his whining next year... not that I'm irritated or anything
), but he had no concept of the medical fraternity system anyways.
Med frats are basically set up for gathering old notes/ books/ tests (tho not so much at UTMB anymore, cuz the PBL tests are all sequestered now), cheap housing, study groups, and letting off steam. Everyone I've known that lived at a UTMB frat said that it's a very supportive system. They also tend to have the best parties... tho these are always scheduled AFTER the big exams.
While it's not for everyone, the frats (coed and non-coed ones) are a pretty reasonable housing choice at UTMB. From my understanding, the main catches are that you don't have much privacy/ ownership outside your room (in the common areas), you might hear your neighbors (but in a med frat people are strongly encouraged to respect the study needs of others), and there are probably yearly frat dues on top of the $350/mo rent.