Salton Sea is just a day trip from San Diego
Birds are good in summer (in spite of the heat) -- late July starts migration southward for shorebirds, and there are some interesting birds post-breeding from Sea of Cortez (Yellow legged gulls, Gull billed terns, etc)

Ramer and Finney Lakes always good.

http://www.southwestbirders.com/swb_...salton_sea.htm
and Poe Road on the SW side of the lake...