Perry – The zip code specific monthly median can vary by 20% or more from month to month. This is called statistical noise. Drawing a conclusion from a single monthly number is dangerous.

Some examples from the same data source cited above:
April 2007 YOY median Price Changes

Bay Park (92110) UP 26.0%
Carlsbad (92008) UP 9.8%
Cardiff (92007) UP 31.6%
Del Mar (92014) UP 20.2%
Ocean Beach (92107) UP 2.5%
Point Loma (92106) UP 9.5%

Knuckle-headed conclusion :
Wow ! All those places near the coast that I want to live in have gone up.