Best Off-Leash Beach: 
Dillon Beach. This private beach in the northern part of Marin is very well maintained and allows dogs - assumed they are under voice control – to be off-leash between the tide line and the water. From the parking lot to the high tide line the leash is required. There is a $10 fee per vehicle for regular day use. $15  on weekends and holidays.
1 Beach Avenue
707-878-2696

Best Remote Beach:
Kehoe Beach, Inverness. This quiet, least accessible beach in Marin is located north of Point Reyes Station. Due to the wildlife, leashes are required. Directions: From Inverness, drive Sir Francis Drake Boulevard to the fork. Turn right on Pierce Point Road and drive about four miles. Park at the roadside and follow the signs about a half-mile to the beach.
415-464-5100

More Pooch-Friendly Beaches:
Limantour Beach, Point Reyes: Not so quiet as Kehoe Beach, but most people prefer this beach. It is a very beautiful, big beach. Signs show that on some parts of the trails, dogs are prohibited. You may walk with your dog to Santa Maria Beach.  Directions: From Highway One, turn between Olema and Inverness onto Bear Valley Road. Look for Limantour Road and turn south all the way to the beach.
415-464-5100

Upton Beach: In the northern end of Stinson Beach, where private houses are built, leashed dogs are permitted. Dogs are also allowed in Stinson Beach’s picnic area by Eskoot Creek.  Directions: Take the Beach exit from Highway 1. Turn right to the parking lots and park at the north end. Go right at the sign “no pets allowed on beach”. Where the private houses start, dogs are allowed.

Dogs are also permitted on Muir Beach, Rodeo Beach and Lagoon and the North and South Point Reyes Beach.