Lots of places to ride in San Antonio. Bring air conditioning!
In the past 6 months we have had numerous motocross tracks pop up. One, Cycle Ranch will be hosting a 4 Stroke National at the end of September. Having ridden at some of the then NESC tracks in your area long ago, my comparison of Cycle Ranch is that it is better than Southwick already. We also have a riding club that leases a huge ranch for riding and holding hare scrambles. You have to join the club for approximately 120 a year and you get 7 day a week riding access. There is an active Texas State Hare Scrambles Series that is usually 12-16 races and a Texas State Enduro Series as well. Terrain here is pretty varied, but tends to be on the sandier side of intermediate. We also have a couple of series that lean more to my addiction, vintage motocross. Let me know if you need more info and let me know when you arrive.