I was born and raised in SA. I've been busy with work, but did find a couple of links for you:
http://www.naturalbridgecaverns.com/
It's a big cave that's north of SA, but a welcome break from the heat
http://www.accd.edu/sac/asl/default.htm
This is a link to the ASL program that I graduated from last year. Sara Filippone should be able to let you know about any Deaf events going on while you're there. The lab is open to the public, so you can meet some of the local Deaf.
I should warn you that SA summers are blazing HOT. They've already had 100+ degree days. For July, bring plenty of sunscreen and aloe vera. Bill Miller's is a local BBQ chain with delicious ice tea and some good eats too. There's a restaurant downtown called Mi Tierra that you may want to go to for Mexican food and pan dulce (sweet bread). The Tower of the Americas should be open again by then too. Enjoy.