As I mentioned a while back, I took a vacation to San Diego a couple of weeks ago. I figured a couple of comments were in order:
First, there is a light-rail system, called the Trolley. Started in 1981, the Trolley is now 51 miles long, but of course, since it's a transit system built into a preexisting city, and a spread-out one at that, its utility is limited. Some of the stations don't seem to be close to anything, in particular, and you can't get to the beach or airport by trolley. I had a difficult time understanding the termination of the Blue Line and Green Line at Old Town. The Blue Line comes north from San Ysidro and terminates at Old Town, while the Green Line runs east from Old Town to Santee. I'm sure there is some traffic-pattern reason for doing so, but I have no idea what it was, and it was inconvenient for me, thereby making it a bad thing...
According to the Wiki article, plans are underway to run a line up to La Jolla, which would have really cut down the time on our trip to the UCSD campus. We bought the four-day passes for $15, which were a decent value considering we stayed (relatively) close to a trolley station and the passes are also valid on the bus.
Part of the Old Town station.
The other comment I have is on Petco Park. We went on the tour (very entertaining and informative). My favorite feature of the park is the integration of the historic Western Metal Supply building... followed up by the fact that Padres owner John Moores (who got his start in software in Houston) owns pretty much all the buildings around it.
All in all, despite the needed improvements to the transit system, San Diego is a great city and I hope to be back sooner rather than later. (And hey, compared to Seattle or Houston, it's tough for me to really say anything negative about transit!)