Glad you're visiting Texas!
The only time you'd be able to OC in Texas is when you're actually engaged in traveling, which is the process of getting from point A to point B; once you arrive at your destination in San Antonio, and for the duration of your stay there until you set out to leave, OC won't be a legal option. However, your Nevada license is good here in Texas (unlike ours in your state ), so you're all set to keep carrying concealed. The off-limits list, etc., for Texas is available at: http://www.handgunlaw.us/states/texas.pdf
A note from my remembering about Nevada licenses - y'all are restricted to only carrying certain semi-autos while concealing with your license (correct me if I'm wrong, I think they're listed by serial number, right?); however, that doesn't apply here in Texas, since we don't have a parallel statute. If you have a semi-auto endorsement from Nevada, you can carry any semi-auto you want while you're here. Enjoy your stay!