+1 on Big Rock. Sponges "generally" welcome, but usually get the standup's scraps. Usually about 20 people competing in a takeoff zone that accommodates 2 people. Another reef eating scenario....super steep and shallow.
Please note that when I say "generally welcome", it doesn't mean that the lineup is waiting with a lei as you paddle out. It only means that surfers and spongers have a tense coexistence. Marine St. is really the only true sponge spot.
Imperial Beach (IB) is also very good for sponging, and the crew is mellow. IB is similar to OCMD, kinda like 56th St. on steroids.
DISCLAIMER: I'm not a sponger, just trying to hook up a Right Coaster.
Hehe, holla at me a week or so before you come out. The surf should be nice and big in January. The spot in the pic in my Avitar is actually one of those "Bodyboarding" spots, although when its firing, the standups take over. But I know of quite a few streches of beach where laydowns and standups can live in harmony. But like others said, if you are more on the beginner side, you should not be at these spots. They are slab reefs that hollow out and dump into very shallow water.
If you are more at the intermediate level, you can just come down to Ocean Beach and surf with me there. I surf the pier a lot in OB, and right to the north side, there is a few peaks that are sponge and swim only. So, you can line up right on the edge of the surfers and have TONS of waves to yourself. Otherwise, we can surf up between Avalanche and the Big Jetty, that whole stretch is kind of surf/sponge through the winter... The waves in OB offer plenty of action, really fun waves, always size in January, but again, assess your skill level, and if you are not pulling into big empty tubes on the biggest days back in OC MD, you have no business at the Wedge, Windansea or any of the above mentioned....
Anyway, those are some tips, but closer to your trip, you should just PM me and see whats up. I live in OB and work in La Jolla, so I usually surf all up and down that 8 mile stretch...
I will say, I havent sponged since like 1992, but I can at least take you out to some places and prtect you from the stink eye. As long as you arent a goober =)