Mildred Falls is the highest waterfall in San Diego County (by far). It is highly ephemeral though, and not flowing very often. There are a number of (artificial) ponds on private property above the falls that need to fill to overflow first, as well as a good number of natural rock pools in the creek bed. After the very wet winter of 2010/2011, the falls were flowing well into June.
I made this photo in the late afternoon. I waited until the entire fall was in the shade to get this 15s exposure (stacking a Polarizer and an ND8 filter, and stopping down the lens beyond reason.)