Where can I get cheaper LTE w/iPhone 5 in the bay area
StraightTalk runs off of AT&T's network and has an unlimited data plan for $45/month. I'm not sure if you can get LTE with that, but you can definitely run 4G (HSPA+).
T-Mobile will soon have 4G HSPA+ in most major cities, and they do an 100 minutes/unlimited data plan for $30/month.
Personally I'd rather have unlimited data on 3G/HSPA+ than LTE with a bandwidth cap.