If you are driving down Highway One south from San Francisco then make sure you stop off at the Pigeon Point Lighthouse. Follow the signs to the lighthouse and hostel. The area was pretty deserted when we visited, though I understand it gets pretty crowded at the weekends as it is a very scenic place.
One of the tallest lighthouses in America, this 115 feet high beauty was a stunning white against the blue sky. The interior has been closed to the public since 2001, and they are currently trying to raise fund for its restoration.
Wander around the lighthouse to the edge of the cliff and you may spot some sea lions sunning themselves on the craggy rocks just off the cliffs. A great place for coastal views and photos, just don't go there if a tsunami has been forecast - apparently it is in the "Tsunami Hazard Zone".
If you fancy staying overnight in the area there is a hostel located right at the lighthouse.
If you've come this far you're going to want to visit the beach. Pescadero beach is a great beach for a picnic with someone special or with friends and family. When it gets hot in the bay area people head to beaches like Pescadero with their food, drinks, frisbees and beach chairs to cool off a little bit. You'll find a few picnic tables as well as a bathroom. You can easily escape the crowds here by taking a littlle walk away from the main area. You'll have no problem finding some peace and quiet here.