Monterey (and Carmel, and the Monterey Peninsula in general) is wonderful, but it is a minimum two-hour drive to or from SF each way, and can easily take three (or more) if your timing is bad (i.e., get stuck in commute traffic), and/or a random accident clogs your chosen route, etc. And the traffic can be bad on pretty much any portion of the route -- not just the parts closest to SF.
Napa and Sonoma Valleys, OTOH, are only an hour drive from SF (again, can take longer depending on time of day, route, etc.). I think if those are on your bucket list anyhow, you should go to that area, and save Monterey for another time.
Or perhaps even just stay in SF the whole time; plenty to see and do.