Drive up 101 to park at the meeting place on the outskirts of Petaluma. Ride your bike on Bodega Avenue across the rolling hills of southwestern Sonoma County in a 38-mile round trip to the seaside town of Dillon Beach. Stop to pick up sandwiches in historic Tomales. Dillon Beach is on the ocean and looks across Tomales Bay at Point Reyes. See sprawling farms along the way and surfers at the destination.