My memory is foggy but if I remember right, after you pass Charles Krug Winery (its on the wine tour maps if you can't find it, and stop off and try some of their stuff) and go about 2 miles, there is a mjor turn to the right. Go through the small town , and you'll see a large hill just past the town, drive up the switchbacks until you get to the crest of the hill. At the crest there is a pullout on the left side of the road with a trail just behind the pullout. Take the trail up the hill doing some switchbacks for about 30minutes and you'll get to the first climbing area just off the trail which has a few climbs between 5.10b and 5.11bish. If you skirt around to the left there is more sports climbing in a more moderate range and about 20-30 minutes past that columner basaltic region for cracks.
If you take a right instead of a left at the first climbing area, JUST up the trail/road is another sports climbing area that has stuff between 5.10 and stiff 5.12d.