I don’t have any specific data for Altadena (or for any city for that matter). However, according to http://www.dqnews.com and the LA Times Sunday Edition Charts which track the median, the median price in Altadena is down 17.4% to $580K or $469 Sq/ft. Of course, the median has huge limitations, but the decline is starting. And as mentioned on this thread, the wave is coming.
I would like to buy in San Marino, but it just seems way out of reach at this point.