A really pleasant bike ride, along some of the most well-trafficked bike routes (for roadies, at least) around, guide you up and through the manicured neighborhoods of Marin, until you turn off onto Sir Francis Drake for a bit of climbing and a bit of country. A neat (dirt) bike path takes you off the last stretch of less than ideal road, and leads you right into the campground. Look for it on your right about a mile before the park.
Camping at Sammy P. is akin to pitching a tent at Muir Woods: giant redwoods, lots of historical charm, and plenty of people (during the warmer months). Luckily, they have a pretty nice hiker-biker area in the center of the park, set up and back a bit from the other sites with a fair amount of room and a variety of sites [edit: this site is now a "restoration" area and the hiker-biker is corralled in a decidedly less ideal location down the park road... oh, the golden days of yore. BUT THOSE REDWOODS, EH]. You can pitch your tent right next to a giant Red, make a blazing fire... and is that a raccoon?
Yes, talk to any biker who's camped out there and you'll get a storied account of the "crackcoon" issue. Watch your food, make sure it's within an arms reach, and get all your edibles and scented stuff those crafty critters might want to explore in the metal lock box. True story: a raccoon snatched two packs of fancy peanut butter cups (for smores!) from the picnic table we had our backs turned to at twilight. Just be smart and think of it as part of the adventure -- there is too much goodness there to let it get in the way of a great park and a good time. OH, AND HIT ONE WITH A BIG STONE FOR ME! - Nick
On the return you hop on the same route as you came, but there is also the option of catching the Larkspur Ferry back to San Francisco and BART. Perfect if you want to mix it up for a leisurely weekend return or if you run into difficult weather.
Outbound Route from San Francisco
Homeward Route w/ Ferry (YES)
Food and Groceries
Lagunitas Grocery and Deli - superb deli with great sandwiches, ample beer selection, and lots of groceries. The closest and best food / drink stop to Samuel P. Taylor. Good prices too. Open 7:30a - 7 everyday. [Aside: Sometimes there are TYPE A ROADIES training for the Life Cycle who aren't very nice there. Mean people on bikes suck and don't understand bike camping, beauty, or nature-- their loss, but not missing em'!]
Good Earth Natural Grocery (Fairfax) - a really impressive organic/ natural market with an equally grand salad bar/deli/hot food/juice bar area. A great place to stop for lunch or to pick up veggies and groceries for dinner.