Mango Bills itenerary is a great one. Leo Carrillo campground is amazing. You could end up doing a lot of driving for not much surf as that area is not very consistent in March/April. If you start out in SD I can lend you a cooler, stove, camping chairs.... Stuff that would be hard to carry on a plane. You could also easily spend the whole time between San Clemente and point loma and surf a different classic break every day. I'd suggest that you stay flexible and then go where the waves are. Even if you rent a van down here you could still bolt up to Malibu your first night and then work your way back. And if you want to drive a little more there's always Rincon which may be more in season.