Looks like I'm the first norcal rider.. I live south of the golden gate, so I have the most experience with that.
From SF, I'd start by heading south on 35 (skyline) and take that to Alice's restaurant. That's a big biker hangout that's part of the local history - good food and on a weekend there's tons of bikes there to checkout. From there, there's so many options, but my favorite is usually 84 to pescadero or 84 all the way out to 1 and then take 1 south if it's a nice day you can ride 1 along the coast and enjoy the ocean views for quite a while. Head back inland when you start to get near santa cruz by taking bonny doon rd or if you don't mind a little bit of traffic you can take hwy 9 from santa cruz and ride that all the way back to the junction of 9 and 35.