Ah heh... you are going to the largest comic convention in the country. Expect long waits, tired feet, and every hotel in San Diego to be sold out. And sadly, aside from the convention exclusives, there won't be much in the way of GI Joe toys to be found. You can still find the comics here and there, but the toys show up in maybe 2 or 3 booths nowadays. It's a far cry from what you could find 10 years ago, and veeeeery different from when I first went in 1997.
Well I know the lines will be long, but I was looking for real insight to costs for like hotels, transport, food etc. I have never gone and would like to go just for the chance to people watch. I am not really into getting autographs, wouldn't mind listening to the lectures though.
Even the lectures require getting into the room well before the panel you want starts. Transport and hotel costs I can't really speak to - I'm close enough to drive there, and I have relatives in the area I stay with. However, if you don't mind crowds, you can try getting a multi-day pass for the red trolleys that cross-cross downtown and outlying areas. They're very reasonably priced, and there are stops just outside the convention center. If you're staying downtown, expects hotel rooms in the $200/night range, and food at the restaurants around there at $20-25/meal.