We rented bikes from Blazing Saddles to ride along the bay, cross the bridge and have lunch in Sausalito, and it was perfect.
No obligation to book, but you save 20% if you do it online, no need to book the day before if you are worried about the weather, we booked 1 hour before!
Fast pick-up and drop-off, very welcoming and friendly staff.
Good quality bikes, helmet and lock provided.
In addition, they recommended a restaurant in Sausalito, "Joinery": we were afraid it was a tourist trap, but we went to see it anyway and it was really good, free drink with the menu given in the morning.
Please note: they give paper tickets for the ferry return which cost $14. If you have the Cliper card or even if you don't, download in 2 seconds and you have the return for $7!!
I recommend if you want to rent bikes in SF.