I think some of the agent response is responsible in that nobody know and it depends upon your goals and circumstances. It does help to be in a good school district even if you don't have kids. Although crazy expensive, the mission district (excluding the Gomes redistrict risk area) and to some extent the Warm Springs area are not seeing huge price declines. Look at the foreclosure tool on sfgage.com and you can see a vast difference between fremont and oakland and if you dive further down you can see a difference in foreclosure activity between different zip codes within Fremont. This would provide a cushion, but not a guarantee.
For example, I sold my home in El Sobrante (crappy schools) in 2005 for $450000. It is now worth $300,000. I bought my home in Warm Springs for $720,000 and while off its highs, is still in the $730,000 through $750,000 range. Schools make a big difference. While this is anecdotal and only one person's experience, it might help you in your decision