I have only been one year (in 2010) because it is expensive so here are my views of the camp from that year:
1) It's a generally casual environment except on talent show days where competitors wore their performing attire. You can dress however you like but most people dress in street clothes.
2) I believe that anyone with enough money is allowed in, but on the first day of camp, they assess your performing abilities and sort you into the proper difficulty class, so you don't have to worry about being with beginners (as long as you're not a beginner, which I don't think you are). The classes are split between close-up and stage (which you get to chose which one you want to be in for the remainder of the camp) and within those categories are different levels of ability (generally beginner, intermediate, and advanced, which you get sorted into depending on how well you perform in the assessment).
3) When I went, I was in the stage class and I'm assuming you're going to want to be in the close-up classes, so I am speaking for the stage magicians. Just bring any of the "classic" or "typical" props like cards, spongeballs, coins, etc. Also bring anything you need to perform in the talent show (if you're competing) and anything you may want to get help on. As for raw materials, they're not necessary unless you plan on bringing trick which will need them. I don't think that instructors would tell you to do anything if they don't have the equipment for you.
4) I don't have a mohawk but I think you could manage to keep it. When I went, there was a guy who had a mohawk for the entirety of the camp. For the "older" kids, there is no strictly enforced bed time and there is no enforced waking up time. Instructors wake you up at 7 and you must be ready to go to breakfast at 7:30, I think. If that's not enough time, you could get up before 7.
I hope this helped and you are able to go to camp because it's a great experience. Just remember to bring a notebook because what you learn will be valuable. You'll be surprised how many kids don't take notes; they'll surely forget most of what they learned in a year.