For rentals, try Blazing Saddles, as they do have some road bikes. Mike's Bikes also does rentals, but maybe only in Sausalito. You have to ride across the Golden Gate Bridge while you are here. From there, you have many choices, but two favorites are (i) if you like to climb, go for Mt. Tam or (ii) if you prefer flatter riding, go for the Paradise loop to Sausalito and Tiburon. Both loops are somewhere around 40 miles RT from SF. If you get tired, you can catch a ferry back (or partway back) if you are on route (ii).
Enjoy your trip!