If you're in Houston, you do realize that city will get LTE from Sprint by the end of the month, right?
Check Sprint 4G Rollout Updates, they might even help you out with launch dates.
If you want to leave, nothing is stopping you, but you'll never get LTE either. HSPA+ is OK, it's just not the show stopper LTE is.
RootScore Report for Houston – February 2012 | RootMetrics
Sorry but AT&T and Verizon are going to outgun T-Mo bad for a long time. Sprint will be in the same ballpark when they flip on LTE. What about T-Mo? Negatron on LTE until 2013.
T-Mobile also has the highest drop call rate in RootMetrics testing in the Houston area.