If you go to San Diego or Southern California, I can tell you that the outlet in Las Americas by the Mexico border isn't very good. It's alright in size, but it's clearance section is pretty worthless. The Carlsbad outlet (right by Legoland and the flower fields) is the one I used to work for. It's nicely sized and is in a nice outlet mall (they also have D&B and Juicy and many other outlets) and it has a better clearance section.
I live in TX now and have to say that the San Marcos outlet is the best one I have ever seen. It's about 3 hours from Houston, so if Houston is 7 hours away from you, then you're looking at approx. a ten hour trip.
San Antonio is very pretty. The Alamo is great, and the river walk is SO pretty. Not too far from there is also Natural Bridge Caverns. I made my bf take me there when we went. It's this huge underground cave system with all these stalactites *sp* and stalagmites and beautiful rock formations. It is totally worth the trip to go there. Plus there is also some kind of Natural Bridge wild animal park around there somewhere too I think. (I can't remember, but I've seen the signs for it.)
There is a lot to do in San Antonio and it's surrounding areas. I believe San Marcos is about an hour from there. (I think, could be wrong.) Plus there is also the Round Rock outlet which is within an hour from San Marcos too. I've never been to it, but have heard it's okay, just not as good as San Marcos.