As suggested, from Winters take 128 toward St. Helena/ Rutherford. Before reaching Rutherford take a right onto Silverado Trail toward Calistoga. 128 is generally a good road, with some shoulders, but traffic is light. Silverado Trail is a good bike route. Nice shoulders. Silverado Trail bypasses the traffic on 29, which is the main road from Napa to Calistoga and is heavily traveled with wine tourists. Once in Calistoga get yourself to Calistoga Road (also know as the Petrified Forest Road) toward Santa Rosa. About a mile on this road you will want to take a right onto Franz Valley. You will not want to take Calistoga Road all the way to Santa Rosa. Hell, I get nervous when I drive that road - narrow and zero shoulders. Franz Valley is very lightly traveled. Franz Valley will take you to Mark West Springs Road. Mark West is generally okay. Since you want to travel the Coast I suggest taking Mark West Springs all the way to U. S 1 where you can pick up the Pacific Coast Route (Adventure Cycling has maps). Mark West changes to River Road on the west side of U. S. 101. River Road will take you through Guerneville on the way to the coast. I have biked this route, along with others in this area, and this route bypasses some of the more pucker factor roads, be it traffic or just rotten roads, while getting you where you want to go. Hope this helps.