This is the one my firned told me about and I called:
http://www.goldengateparkbikeandskate.com/aboutus.html
Its $5 an hour and Tim, the owner's son said, that they are usually
busier in the mornings, so sat afternoons at 3/4pm they'd have more
bikes. Also, if you talk to his dad, he can probably give a group
discount off that $5 an hour.
Also, I think they have dual person bikes. Other places are liek 32 for day.
good luck dude.