There's a nice article in the Press Democrat on longtime Hopland wine bar proprietor (and organically grown wine provider) Bernadette Bryne, of Sip! Mendocino. The former Fetzer PR person opened her own wine bar in Hopland in 2007 and has been a great source of information for locals and visitors alike.
If you're passing through Hopland, stop in and get acquainted. Sip! Mendocino is the perfect place to start your tour and it's the most convenient place (besides the Ukiah Food Coop) to find organically grown wines.