First, some tips:
1. Get your tickets in advance. We had three days passes, so we had no problems. But Saturday sold out, and many people did get turned away. They had over 100,000 people on Saturday.
3. We stayed about five blocks away and walked. That was easiest. Parking near the Convention Center was a mess. We also could have taken the light rail, but we wanted to walk. We didn't try to drive in because it was just insane.
4. About half the people were in costume. You will see everything. We saw dinosaurs, daleks (a wheelchair costume), anime characters, movie characters, etc. There were dozens of Doctor Whos. Girls seemed to gravitate toward quasi-sexy anime characters, guys seemed to gravitate toward things in armor. There were people dressed like several musicians -- Prince, David Bowie, Meatloaf, the Beatles. There was a Carmen Sandiego. Tons of Star Trek, Star Wars, Dr. Who, anime. The most common costume was Deadpool for males and Harley (from Batman) for girls. That said, weight, body type, gender didn't matter, everyone was cool with anything. Whatever people wore, everyone liked it... and the self-made costumes were the most popular. I didn't hear one negative word from anyone all weekend about the costumes. And everyone we ask to take their picture was thrilled that we asked.
I would estimate the crowd was about 50/50 male to female, of all races, and there were lots of father/son and mother/daughter combos there -- in and out of costume. One of the cutest moments was a father/son Batman and Robin walking down the hallway together.
If they have a super special guest (like Stan Lee) and you want to get an autograph, it would be best to buy a VIP pass if they have them. There were only about 20 people around Stan Lee with VIP passes, but then well over 5,000 tried to see him at the public signing.
6. We enjoyed walking through the sale/merchandise floor (I would guess it was six high school gyms wide and three long). The seminars were great too -- wish we had gone to more of those. But the coolest thing was just seeing the costumes. For that, you can walk around, OR you can find some spot in the main hallway and everyone will walk right past you... several times. I estimate we walked about five miles a day, by the way. So keep that in mind. There were girls there doing it in major heels and I felt pretty bad for them by the end of the day. But you really can just find a place to sit and see a large part without all the walking we did.
Finally, some thoughts.
We had an amazing time. It was really neat to see so many people just enjoying themselves. Half the crowd (or maybe even more) was women. A sizable chunk was black or Hispanic. There were some obviously gay people there too. All ages were represented as well. There were parents with kids, groups of friends, and even some single people. And the best thing of all... everyone got along happily. There was no anger. Everyone was polite and courteous. Everyone was happy to see everyone. There was immense creativity too. Not only in the costumes, but in the products people sold or displayed, and in hearing people talk about whatever "project" they had going in their lives (people walking around as well as people on stage).
So I highly recommend going to Comic-Con and just being a part of that world. It's the way society should be, and it shows how society can be.