Rescue 51 I have noticed that also and I'm not from San DIego but I am a fan of the San DIego fire department and I know that the San Diego Fire Department was one of the few West Coast fire departments that was still using some Aerial Platforms in the late 1990's and the early 2000's. At one time they did own 4 Tower Ladders and they had a Snorkel running as Truck 14. When they went to solid red fire engines and started buying their current Pierce Aerial Ladder Trucks they have seemed to forgo purchasing any Tower Ladders or Snorkels. I know that San DIego was having serious financial problems and budget shortfall's during the recession and I also know that San DIego was running behind in building new fire stations however over the last few years it is attempting to catch up with buiding some newer stations that have been called for. Perhaps they were only buying straigtht aerials because they were on a tight budget and the straight aerials were less money then a Tower Ladder. They also could have had some weight problems with thier tower ladders and they could have had some clearence problems on some of the streets or in some of the fire stations.
This is only speculation however as I am not from San Diego.