There's another thread about almost the same question going right now. http://www.fodors.com/community/united-states/san-francisco-area-what-would-you-do.cfm

I would say absolute minimum would be two days each (coast, SF, Napa/Sonoma. I did a trip last spring that included three nights coast, two wine country and three SF. Could have used more but I would do it again in that time frame. Here's my trip report from that trip - and link to the photos - http://www.fodors.com/community/united-states/central-california-coast-pacific-coast-highway-napasonoma-and-sf.cfm

I think two days each as an absolute minimum is right. But I would choose just Sonoma. It's less crowded and you can see more and eat more and generally enjoy your time more than in Napa in that short timeframe.

Two days in Sonoma and Napa is enough for me--I don't see a problem unless you pass out from too much wine. Pick a place for two nights and explore.

The drive from San Francisco to Big Sur is not pleasant unless you go on Highway 1 through Half Moon Bay. Take the scenic route to Carmel (125 miles/2 1/2 hours), spend to nights in there, and use it as your base for checking out Big Sur.

Enjoy, HTTY

I live fairly near both Big Sur and the wine country.

I would have to agree with NewbE on Sonoma. Lodging rates are sky high in both Napa and Sonoma. Check out Glen Ellen as a lower priced alternative to Sonoma town.

I'm doing a cheapie 3 day visit next week to Healdsburg, for lodging ~ $50 a day. In the summer, the same place is around $190 a day.

Weekends are not the time to be in the wine country. http://www.sonoma.com/

Drive from Napa/Sonoma the "back way' to Carmel/Monterrey/Big Sur and avoid the Bay Area traffic. Check out the maps.

As a resident of the Bay Area I go to the Napa or Sonoma area on a day trip. As a visitor wishing to see more, I think that one overnight is sufficient given your short time in the overall area. Leave SF around 9 a.m. one day and return in the late afternoon or early evening and you will have had plenty of experience in either the Sonoma valley, which I recommend for its historical sites as well as wineries, or the Napa valley.

Thanks, everyone, for the wonderful tips. Would Carmel and the Big Sur be crowded in August?

My husband and I did this exact trip last April, and it was phenomenal. We only had a long weekend, so we flew to San Franscisco on a Friday night and drove to Big Sur Saturday morning. We had enough time to drive to the Bixby bridge and to look around Carmel and Monterrey. Then we drove to Napa Sunday night and spent Monday and Tuesday at the wineries. We definitely could have spent more time at each place, but it was enjoyable nonetheless. I highly recommend Hotel Yountville. When we go back, we want to stay in Healdsburg (in Sonoma). I probably preferred Sonoma to Napa as well, but if you've never been, Napa is worth visiting.

We were in Big Sur/Carmel for the weekend of the Big Sur International Marathon, and even there were a lot of people, it didn't affect our enjoyment. I would imagine that the weekend we were there is the busiest weekend of the year, so I doubt August would be too crowded.