Hi Usersatch,
I live in Chula Vista between SD and TJ. I've only lived here a couple years and I do my railfanning elsewhere for the most part. There is lots of trolly and commuter/Amtrak action but that doesn't interest me like freight. Because of all the passenger activity most all freight action happens at night. But the good news is if you are going to be at the convention center the freight and trolly yards are right there, just south of the convention center. You can usualy catch something being built or torn down in the BNSF yard. You can also watch the trolleys comeing and going as well as the Coasters laying over in the SDIV yard.