Thanks for the advice! We went to the non-profit Pedal Revolution in SF, and the cheapest bike with more than one speed was $450, while Walmart sells road bikes for $170. If we need to pay $450 we will, but we just wanted to explore our options. The co-op in SF is unfortunately only open for about 4 hours on Saturday and not at all on Sunday. Since we're only up in the city on the weekend, it's just been tough arranging our schedule so we can get there during their open hours. I'm also not sure if they have many used bikes for sale. We are going to try Performance bikes, and we were looking at Bikes Direct, too, but we were hoping to go somewhere where we could do a little test ride.