A couple of years ago I rode south from SF to SLO in December. It was warm during the day and cold at night. Frost on the ground. Then the day I finished, it rained for three months, wiping out a couple bridges and causing a major landslide. And the day before I started, there were a couple days with 60 mph winds from the south. So, you may get lucky or not. I liked the hostel at Pigeon Point, which is a day’s ride from SF.