In my opinion, your best asset is Texas residency. Texas schools are cheap & plentiful & will give you in state preference...but Texas schools are competitive. You might get lucky with a 3.2/28S, but I think you're right to plan on improving your numbers.
Since the TX app opens on May 1, I think you should apply on May 1 with whatever assets you have on that date. You can indicate a future test date and future academic plans when you apply, but those future plans won't necessarily have a large impact on your app. By contrast, imho, waiting to apply until you have a better MCAT score later in the summer wouldn't be worth losing the early app advantage. So what I'm suggesting is that if you have a nicely packaged, compelling, interesting and early app you might get somewhere with your existing stats - you might get an interview or two, and you might get serious consideration at TCOM. I think you'd get nothing with a late app, even if your MCAT goes up.
Between now and then, make sure that your letters, essay, and extra-curriculars are impressive. You have almost 6 months - what holes can you fill in that time?
I have a high opinion of the postbac program at UT Dallas. They have good structure and you can take a lot of upper div science. In your shoes I'd do this program instead of going east for an SMP. I think an SMP would cost you an additional year unless you leave TX for med school. Which I hope you don't have to do.
Lastly, don't retake the MCAT until you have a large pile of evidence that your score will improve. Half of retakes get the same score or a worse score (see aamc.org for the stats). If you want your score to do up, you have to do a bunch of work - take a prep course (or a different prep course), and take *every* practice test. Plan on losing a point or two on the real exam vs. the practice tests. That said, 28S isn't that bad, but if you can get a better-than-average MCAT (32+), that's a great counterexample to your GPA (which you literally can't get up over the average 3.6+).
Best of luck to you.
