IMO, San Antonio has its own vibe. While you can see parts of Austin here in Houston, SA maintains its own. Everyone I know there is married with kids, so it is quite family oriented. They adore the Spurs and love the Cowboys, but many fans are bandwagon and will flip.
I don't really know much about the culture, but I do know it is a city on the rise. I do like the fact that it has maintained its own uniqueness.