Just shooting from the hip here:
I think the prices are remaining flat or somewhat stable in Norht County because they have a lot of newer, big homes that have more flexibility in their prices. Aviara/La Costa in Carlsbad and Encinitas Ranch in, well, Encinitas (I know, duh).
Anyway, what I see in my neck of the woods is newer homes (1999 and on) selling next to much older homes (1975 – 80) but they are selling in the same range (750k – 1 mil). Those older homes have to drop in price sooner rather than later.