Try http://www.vrbo.com (Vacation Rentals By Owner). I’ve used vrbo frequently and have always found a nice condo or house, depending on what we’re looking for, at a fair price. I’m sure there are plenty of good San Diego options at all the beach locations, and you usually work directly with the owner rather than an agency that tacks on extra fees. Most listings include lots of photos and some have helpful remarks from past renters. I’ve always found that you can bargain with the owners, especially in an off-season month like May. Good luck!
