RE: Houston to San Antonio on I-10?
Sorry to contradict Lone Star BUT, while City Market in Luling is okay (the sausage is wonderful), it's been coasting on its laurels from quite some time, the Texas Monthly rave (awarded back in the late 80s or early 90s) notwithstanding. The best BBQ is in Lockhart--Chisholm Trail on Rte 183N. Lockhart is about 15 mi. north of Luling.
There are quite a few other BBQ places in Lockhart (Blacks and an angry relative spinoff to name a few--skip them) but the hands down winner in that part of the state is Chisholm Trail (on left-hand side, start looking after Wal-Mart and if you pass the HEB grocery store, you've gone too far). Their pork ribs are the absolute best and the brisket is pretty damn fine also; you can cut it with a fork. They trim the brisket well (before weighing) but leave a little bit of fat (because it is so good), the sauce is very good and the sides are excellent, including my favorite--fried okra. Their BBQ sandwiches are big and tasty.
Every year when I go home at Christmas, we always stop on our way back from the Austin airport to Gonzales and pick up a couple of pounds (or more!) of meat to take home. Trust me on this--I'm a born-and-bred Texan, raised on good BBQ and this is some of the best ever. I hope you'll give it a try.
About Frank's in Schulenberg. When I was going to college in San Marcos, we used to stop there to eat on the way to and from Houston and when it was the "old" Frank's, the food and atmosphere was excellent and quirky. Since they finished I-10 in the late 70s, Frank's built a huge restaurant out on I-10 and they went kind of touristy. It's been about 5 yrs. since I last ate there and everyone said their orders were good and because I only order chicken-fried steak (it's the best thing on the menu and I'm always hungry for it when I go home), I can't really give you a 100% recommendation other than to say, if you're hungry for c-f steak and can't get to Austin for Threadgill's, then that's the place to stop. BTW, don't bother with Berger's Smokehouse on I-10, rip-off.