I don't know if this is too late for you since you asked this last week but we've done a number of trips to southern california when we had little money.
We always seem to check out Seaport Village- mostly shops but it's right there by the harbor so we walk to that and look at all the ships. The Midway is right there!
The San Diego Zoo isn't too expensive if you can get coupons.
We always take the ferry to Coronado, get off, walk around a bit and get some ice cream and then take it back. Very cheap way to get a boat ride!
Point Loma Lighthouse- beautiful ride up there, some great history to read about and then there's a tide pool in that same area as well that you can check out. Not sure how much it is to get in but it's by the car.
Old Town- lovely shops with live mariachi music playing. Several mexican food restaurants and then the old town jail, general store, doctors office etc. We love to eat a meal there before we head home. We also let our kids pick out some candy from the candy shop.
We went to see the sea lions at the beach in La Jolla. I can't remember the name of it but its a lot of fun.
In carlsbad the strawberry field is opening April 1st, I think. You pick your own. We had a blast doing that a few years ago. Right next to
Legoland.
There is so much do and see without you breaking the bank. Hope that helps some. Good luck!
