Yeah historical numbers are available and you can get them month by month. It would take me awhile to do that so I will have to pass. I would have to do a month by month search on SOLDS. If I had less on my plate I could do this for you but right now I am swamped.
However, you can go to dqnews.com to get the dataquick numbers for san diego on a per zip code basis. Unfortunately the charge you for archives for the past which sucks. I would bet you can get them from the county as well. These would actually be more accurate because they would cover fsbo where the MLS does not.
actives pendings
92118 detached – 110 23