In North County try the nice beach in the north part of Del Mar. You can park on the street just a block from the beach in the "Beach Colony" area. South of Del Mar on 101, is Torrey Pines beach which another good area. The beaches from Cardiff to Carlsbad are all good and have a variety of fishing oportunities. If you are coming south on I-5 towards San Diego, get off at Oceanside (Mission Exit) and go west until you hit the Oceanside pier. That is worth a stop. Sometimes the pier fishing is good with bloodworms or clams for Croaker. It is fun just to walk out and see what's cooking. There is a Ruby's Diner at the end of pier.
Head south on 101 to Carlsbad. South of Carlsbad just before you get to Encinitas, is Ponto Beach. It is a good stretch to fish. Also there is good activity in the inlet to the lagoon depending on the tide. YOu may see someone fishing on the east side of 101 on the inlet.
In Encinitas, at the corner of Encinitas Blvd and 101 turn to the Ocean and you will hit Moonlight Beach. There is lots of parking and you can hike off to the north or south of the parking and beach area and work up and down the beach to find fish. To the south towards Swami's Beach there is some rocky structure on the north side of the point that sometimes is good at high tide.
The whole coast in the North County is very accessable from 101 and is filled with good beach/surf fishing opportunities. If you start early you can hop down the 101 and stop wherever you think it looks good and dip some bait for an hour and then move on. It would make a great intro to the area in one full day.
Just about two years ago I was doing a project in San Diego, and I stayed at a hotel across the street from Pacific Beach, near the pier. This was in late February. I went down a couple of hours before sunset, at high tide. I ended up getting 14 BSP, and got hit on nearly every cast. I used 1 1/2" motor oil grubs with calico cocktail scent addded. Great action for that time of year. The beach was a little crowded, but the water was empty.