Thanks for the info. My trip out to California is all centered around a conference. The logistics are simply that I've got a full day to get from San Francisco to Napa. I thought it would be cool to plot a course that took the whole day to get to my destination. I don't mind biking 70 miles and doing 2,400 feet of climbing, but if I'm going to run into lots of unpleasant and possibly dangerous traffic, that would be a drag.
It sounds like it would be better to get to Napa by ferry, drop my load, and just take a long afternoon ride up north. I have no intention of renting a car at all.
The next two days will be spent entirely inside, probably not ever seeing sunlight.
For the return trip, I have only 1/2 day. I've got to catch an afternoon flight out of SFO, so I'll definitely need to take the ferry back. No options for a trip along the coast, as nice as that sounds.
It kind of stinks to be a working stiff!