The SF Bay Guardian just put out its annual Nude Beach Guide, which is highly recommended reading if you're trying to get naked legally in public (or if you're trying to avoid people who are trying to get naked legally in public). In terms of nude-friendliness, they gave all the beaches in SF County an "A," except for Fort Funston Beach, which was demoted to a "C" because of "dogs" and "gliders." Also noteworthy are the legal statuses of each of these beaches. Basically, they're pretty much all legit naked spots "as long as no one complains and you don't touch anyone." Check it out.
Legit Naked Beaches