Nope (other than the airport) .. but I've been to Austin a couple of times which is about 1 hr drive away - if you get bored in San Antonio Austin has a nice downtown area with a pretty lively night life (good music scene I believe)
Going to a BBQ restuarant is a must in those parts .. I've been to this place which is between San Antonio and Austin - http://www.saltlickbbq.com/ .. it's well worth the trip - make sure you go hungry !
San Antonio is quite a nice place. The main attraction other than the Alamo (which isn't that great) is the Riverwalk. An old commercial canal area that has been done up very very nicely with about a mile of bars and restaurants. Well worth visiting and probably spending most of your time in that area.
Other than that, it's a large American city and not all that great for pedestrians.
We have sorted car hire and are staying near the Riverwalk. So impresses with www.visitsanantonio.com - the savings are huge, saved $80 a night on our hotel compared to their advertised rates. Other great discounts and suggestions too. Can't wait now!
Nice town, all the bars/restaurants are at the riverwalk. Town centre is walkable. The Alamo is interesting also. Is a fairly busy town as is quite popular for business meetings/conventions. Weather should be nice at end of Sept. I stayed at the Westin (up to usual high Westin standards). Found locals quite friendly. Have not been to Austin but have heard good reports about that also