This is the way I like to do it.
Take Hwy 101 to Petaluma. Take the East Washington Street exit and go through town. You will be on the Bodega Highway, about 26 miles from the coast at Bodega Bay. This is the town where Alfred Hitchcock filmed "The Birds". There is a restaurant, gift shop and fish market at Lucas Wharf. You can drive out on Bodega Head for great views of the ocean. Ask for directions.
The next 10 miles you will pass several state beaches, mostly for walking on. The water is too cold for swimming.
You will then cross the Russian River, turn left after the bridge and soon you will be in Jenner.
The coastline which is similar to Big Sur is above Jenner. The road goes high on the cliffs and down into the gullies, with fantastic views.
10 miles from Jenner you will pass Fort Ross State Historic Park. This was an outpost of the Russians during the early 1800's and served as a trading post for otter furs as well as keeping Russian influence in the New World.
Three miles above that, stop for a break at the Timber Cove Inn, which is a spectacular piece of architecture built on the bluffs in the 1960's. The very tall obelisk at the south end of the Inn is meant to be a representation of St. Francis and is dedicated to peace. During the VietNam war, however, it lay in the meadow across from the Inn because it needed a large helicopter to raise it in place and they were all busy fighting a war. Watch the link for a few minutes, the pictures change.
From here you will pass Salt Point State Park. Unfortunately, the day use facilities are closed due to California's budget problems. You may, however, be able to park and walk in just to see it.
Before Gualala you will pass Sea Ranch, a development by Castle and Cooke in the 1960's with clusters of homes in open space. The architecture is quite distinctive.
Gualala is an artist colony of sorts with a very nice Arts Center near the south edge of town and several galleries in the town itself.
This is about 50 miles south of Mendocino, on the coast and passing several small towns.
On your way back from Mendocino, take Hwy 128 at Navarro, 11 miles south. The road follows the Navarro River for several miles and the area is Called Navarro River Redwoods State Park. Much of the rest of the drive, which takes you to Cloverdale at Hwy 101 is through vineyard country.
You may want to make a stop in Healdsburg, which is a cute town around a square with shopping and tasting rooms.
I do not know Mendocino well enough to recommend anything, so we will wait for an expert on that to come in. I am guessing a little less than 4 hours from SF without stops.
Have a nice trip.
Edited: 2:54 pm, August 14, 2011