Just about any of the parks in SA have novice trails (meaning little to no elevation, drop offs, hard angle ascents, etc).
Leon creek, Mcallister, OP Schnapel...all have a wide variety of terrain to choose from. Any would be good. I'd recommend OP if you want to keep things within a certain distance and it will likely dry out faster than Mac. But given the wet right now, I'd recommend staying off the trails at Mac until it's dry. Guys that try and ride the trails when it's wet end up ruining the trails and creating ruts and so forth.
Same goes for any place really...but any of the 3 major parks that folks use would be fine.