Keep looking for the local playground (check out newer subdivisions, apartment complexes, near schools, etc)! If you boy likes ChuckE Cheese, he'd probably love the park. Being in such a large city, you can probably google "activities for kids in San Antonio" and come up with all kinds of things. Do you have a zoo and/or aquarium (zoo for warm, sunny days; aquarium for cool or rainy days)? My girl also loves Petsmart/Petco and will watch the mice, rats, hamsters, and guinea pigs for a good 20-30 minutes. See what membership activities are in your area (Gymboree, kids gym, etc) and ask if they have a "first class free" policy! That could keep you entertained 1 day a week for several weeks (and you may even find a place with a reasonable price that you could join). Some arts & crafts stores have free or cheap activities (see Michaels website).
Have fun!