Water temp is cold now at around 56F so at least a wet suit with jacket is important. But air temps this weekend will be warmer than recently with a high in the upper 60s. Also bring a helmet.
San Onofre is a state beach. There is a $15 entry fee, unless you have a state parks pass.
You may be able to arrive later this time of the year with no parking issues. Often by 10am or so the "dawn patrol" is starting to leave. I should be around at least until noon.
Bring food, chair, etc. you may want and plan to hang out surfing and kicking back for a few (or more) hours.
Drive south on the 5 to Basilone exit, turn right at the end of the exit toward the ocean and follow the road. Look for a right turn past the stop light just before the power plant.Take directions to the surf beach.
If the lot is full you need to join the folks in the dirt waiting area left of the entry station. For each car that leaves the beach one from the waiting area may enter.
Go to the very south end of the dirt parking area near the power plant. I'll have the blue acura wagon and the blue kayak. If the lot is very full you may want to unload gear at the end of the lot then go find a parking spot.