I know you're in the San Antonio area but if your city sponsors a MS150 bike ride for charity fund raising, then you might be able to pick up a bike after that event cheaply, as there will be those that go out and buy a bike and decide never to ride again.
I mention the MS150 because the Houston to Austin event just completed this weekend with around 12,000 riders. Ouch, that's alot of sore muscles.
