You may wish to work with a property management company or a REALTOR, as they can provide a ton of assistance in what can sometimes be a frustrating and trying experience. Not to be a total downer, but there are plenty of rental scams out there, so be very diligent and if something looks like a rat, smells like a rat, and tastes like a rat, it probably is a rat.
If that didn't scare you altogether, you may wish to look at the following sites for possible rentals: Trulia, Craigslist, Backpage, SignonSanDiego, San Diego Union Tribune.
If you opt to work with a REALTOR, they have access to other rentals through the MLS system. If you have an agent doing the right things for you, they will reach out to their vast sphere and try to track down a rental as well (perhaps one not currently on the market.)
One other tip could be to drive around the area that you would like to rent in. Often times, there will be for rent signs that otherwise you would not know are available.
I hope this helps and best of luck in your search. The good news is that while home prices are up over 14.1 over the past year, rental rates are only up .1%. There are various reasons for this, but I will not get into that here.
My brother lives in 4s Ranch and I work that area, so I should be able to help you out, so feel free to contact me.
Best of luck,
Chad Basinger, REALTORÂ®, CPA, CFPÂ®