Time to drive to Austin! I really haven't seen much of anything going on in San Antonio. We're down there once in a while but haven't ever been able to find any machines. There are a few sales on craigslist in the area, though, so someone's around there.
Really, though - do it. It's about an hour drive-ish from downtown San Antonio to downtown Austin. If you're in a hurry Pinballz Kingdom in Buda is closer. Buffalo Billiards and Pinballz in North Central Austin are the places to hit up.