Later than promised... I ended up going on a 200 mile ride out, parts of which I would not recommend but most of it was fun!
As Kevin mentions above, you need to go to Muir Woods early as otherwise you will just sit behind cars for most of the journey. The ones I had were good at pulling over where there were gaps ("turn outs") but you've still got to follow them until the next one turns up. The journey I detailed above started out with a chunk of Interstate but once you get off that the rest of the route to the woods involves a lot of very sharp bends that are very close together, great for honing your technical skills in picking out the right line.
From Muir Woods I headed for Monticello Dam, not following the original route had planned. The I-101 was a bit of a drag , as was route 121, but once I hit routes 12 and 221 the roads got better going up hill and down dale with more interesting bends. These were less sharp than Muir Woods but still fun to ride through. I rode beyond the dam and down the other side and the best part of the journey ended once I hit I-505.
The rest of the ride was on straight roads, not fun although there is a nice series of bends heading south on the route 29 from Middletown towards Calistoga. Not worth heading that way just for them but if you can add them in to a route on the way to somewhere else then so much the better!