I have read that the special trolley passes will be on sale down at the convention center station, but last year I couldn't figure out just where? Is there an actual person in a booth to buy from or are they only available from a machine? Help!
There is the little red booth at the trolley stop in front of the Gaslamp, but it's only open at certain times. You can buy one at the transit store at any time, it's a short walk away from the Convention Center. It's actually sold at a bunch of stations where they promote you park and ride the trolley to comic-con. You can also buy the digital version online.
Do you want it for actual transportation or do you want it as a collectible? Many people think the comic-con pass is cheaper, it's not. It's more expensive than the normal trolley pass. Not by much though, only by a $1 for the 4 day. It's the same cost for 5 days.