Some sites: I’m sure you know about Signonsandiego (web version of the U-T) and/or sdrentals.com (used to be really good, not so sure since they’ve been bought by westside rentals).

There are also various other small property management companies that specialize in managing SFRs for individual homeowners:
renthomes.com, utopiamanagement.com, sdppm.com, cal-prop.com
There may be more that specialize in the areas you are looking.