The little coffee house on the west side of Hwy 1 in Marshall is a great stop. I'm having coffee there tomorrow morning. The whole town takes up about 120 yards so start braking when you see the first building.
I have learned that between Pt. Reyes and Marshall there are quite a few turn that stay damp from the tree cover.
I was lucky enough to have some time on a business trip to San Francisco to ride in West Marin County. I didn't ride the exact route you described (I rode one I found on pashnit.com) and it was incredible. I think I hit more curves in 4 1/2 hours than I have in 10,000 miles of riding in Illinois. If you're ever in the area make the effort to get at least a half-day ride in.
We're hosting a shop ride on this route next Sunday, 4/10. Barbecued oysters, barbecued chicken, great scenery, some of the finest roads in the US. See the Events section on our site, www.marincycleworks.com, for more details. All brands / models welcome.
This is pretty much my regular route. I can offer an alternative if you don't have time to head all the way up to Tomales.
In Marshall, take Marshall - Petaluma Road to the right, shortly after Hog Island Oyster. This road is bumpy, but sparsely populated and lightly trafficed. Head on up the hill a ways, past the farm. After a nifty wheelie bump, there's a dog leg left with small pullout on the right. If you park there, you're able to see the entirety of Tomales Bay. It's one off my favorite views in the county. There are generally deer in the pastures below.
From there, head further up the road, along the ridgeline and down the other side. You'll pass a couple farms and then you'll see the Marin Motocross club's park on the right. Sometimes, you'll catch the peewees out running the little dirt track and sometimes you might catch the trials guys out hopping around on the logs. Either way, it's a nice way to spend a few minutes.
From there, continue on Marshall - Petaluma to Hicks Valley. Take the right on Hick's Valley until it dead ends on Pt. Reyes - Petaluma. Take the right onto Pt. Reyes - Petaluma. If you need to pee, hit the Marin Cheese Factory. You can score something to drink there as well.
Take a right out of the parking lot and continue south on Pt. Reyes - Petaluma. As you cross over the ridge, you'll be treated to a terrific view off Black Mountain on the right and the Nicasio Reservoir on the left. Continue on down the road until you get to the stop sign at the bridge. Watch for CHP along the stretch by the reservoir, they patrol with both bikes and cars out there. The fat guy in the cruiser will cut you zero slack, but the bike guys are pretty reasonable.
Take the right over the bridge and you're on your way back to Pt. Reyes St. The road follows the stream bed and the canyon, so it flows really nicely with mostly open corners. There's a blind right that has a pretty sharp hook about a half mile down the road, watch out for it. There's a quick segment with two other blind rights, but they're nice, constant radius with decent pavement. When you get to the end, take a left back onto Hwy. 1 and head into Pt. Reyes. Stop at the Bovine Bakery and have a cup of Really Good Coffee and some fantastic pastries. The bearclaws rock and will be a nice treat for those waiting at home.
If you're coming from 101, you can get off at Lucas Valley Road, take that out to Nicasio Valley, right on Nicasio Valley road (mind the 35mph speed limit in Nicasio!) and then take a left on Pt. Reyes Petaluma. You might want to start at the Bovine as there are usually a few bikes parked there on weekends and the regulars are friendly.
The bathroom in Pt. Reyes Station is at the gas station. Bring a quarter.