I live outside Houston and work downtown, and it is well worth the trip. Check around with your local LQSs and see if anyone is sponsoring a tour bus. My sister did that last year from Missouri, and the fare included one night stay in a hotel on the road each way, plus the night stay in Houston, and several meals. If you do plan to come, make your hotel reservations now, especially if you want to stay in the downtown area. There is good bus service all around downtown, with at least 5 routes that go right by the George R. Brown Convention Center.
If you have a mobility problem, you can rent a Scoot-A-Round. I've done that for the last 3 years, and it is well worth the $$$. Otherwise, as sewgray said, wear your most comfortable shoes. Plan to spend one day viewing the quilts and one day visiting the vendors. You will love it if you're a gadget junkie (like me), because you get to see the latest stuff.