First, I started at the Embarcadero. This was were a special "Con-X" hosted by the E! entertainment channel was going on. Plenty of free stuff and food there.
They had a lot of good guest speakers. Here, Al Jean talked about the upcoming season of the Simpsons. I believe Adam Nimoy was also going to be there later that night, but I was too tired to stick around.
Even though you can't go in without a badge, you can see a lot just hanging around the outside. The Game of Thrones production was holding a panel on the inside of the convention center. On the outside, a group of people doing Game of Thrones cosplay posed for photos on the convention steps. Also nearby was the "Abigail" yacht from the Walking Dead. It had lots of zombie noises coming from it and at least one person was in makeup.
Tons of stuff to do around Petco Park. Here's a sample of the interactive South Park display: