I was just in San Diego (I live in NM) and was very impressed with a nursery in Jamul (I can't remember the name but it's surely the only very large nursery in Jamul, on the 94). I know that's pretty far from you, but it was huge and they had good prices and a wide selection of different things. We got some one gallon olives for $4.50 each!

But, for ease, I would first check your local box stores (Home Depot, Lowes, Walmart, etc.) as they always seem to be the cheapest as long as can you find what you are looking for (for example, I saw a 15 gallon golden bamboo for only $30 at Home Depot). The prices seemed to be around $18 to $20 for 5-gallon fruit trees, and $40-60 for 15-gallon plants.

By the way, have you checked out any of the enormous nurseries along both sides of the 15 just south of Temecula? I used to pass through there on a regular basis and always wondered what they had, as all you could see from the road was a forest of palms. May be worth a try though.

One word of encouragement... you are so fortunate to be in SoCal when it comes to plants... not only for what you are able to grow outside there, but also for what is available from nurseries, and most importantly, for the prices. I had to stuff my car full before returning home to NM, because I would have paid fully 3 times more for the same plants here (if I could find them at all).