Hey there Hedge! We would love to have you out here in sunny SoCal!
I wish I had a more welcome response but cheap and San Diego don't go hand in hand for anything. Great town but expensive town especially anywhere by the water. Going inland is your best bet for cheap. Now if you want to do state parks and hop about every week, you could go up and down the coast from the bottom of Los Angeles to the boarder of Mexico below San Diego for less money however that will take some planning as the coast parks fill up months in advance. Winter less so, so you may be able to do it. Those coastal state parks are lovely! Crystal Cove in Orange County comes to mind.
Good luck!
