For those of you looking to travel to the California Coast, October is the perfect time to go. The weather is perfect as it is before the rainy season and the temperature is mild. It is also my favorite time to visit the wine country in Napa and Sonoma.
Usually October is also when the harvest is going strong but this year with our drought and hot summer the harvest was a little earlier. Don't let that stop you, this is still a good time of year to visit the wineries. If you can I would go mid-week. The crowds are a lot less and you will find it easier to get to the tasting bar and to find a table at a restaurant.
For a day trip I like to make my way up through the Sonoma county wineries, cut across when you hit Santa Rosa and then work my way down Napa Valley. The wineries are up to you but some of my favorites are Kenwood and Chateau St. Jean in Sonoma County; and Grgich Hills and for sparkling wine Chandon in Napa Valley. Look at a wine map and pick your own.
You still have time. The weather should be great into early November.