duude,
When you check the chart make sure to pay attention to volume. Most ZIP codes with sales volume of at least 15 and more realistically 20 sales are down countywide. Several of the high volume ZIPs showing gains on the chart are places I know are getting slaughtered such as 92078 San Marcos. The low volume sales are more volatile and less valuable as a predictor. I don’t believe they are an accurate representation of anything. Also the relatively high volume ZIP’s that are up tend to be in garden spots of the county like Encanto and El Cajon.