As I said we hired a car and drove up. I chose highway one to enjoy the coastal views but virtually all we saw was fog! We did see a wolf on the road just after we crossed the Golden Gate Bridge. Still was an interesting drive. Trip took a steady couple of hours. The return journey a similar time going straight down the 101.
One of the really helpful thing the folks in the Sonoma Wine Country do is make it easy to find where you're going. At every intersection, visitors will find signposts directing them to the various wineries. At the top of the signpost is a designation of the specific varietal the area is known for.
There are literally dozens (if not hundreds) of wineries in this area, from very small to quite large. It's important to remember to pace yourself. And always choose a designated driver. OK, sometimes it's not so much fun to be the DD, but it should earn the volunteer some special rewards along the way. :-)