Other skaters may or may not have their coaches there. I couldn't really afford to pay mine, so he didn't come to competitions unless he had other students there.
I think it is tough to tell if you will be competitive- you just never know what other skaters will be doing until you learn who is your usual competition. Most non-sectionals/nationals don't divide by age class, so you might be up against everyone. (If there are enough for a 'group' who are in a much higher age class, you can try to petition to seperate it. Our state games had an 'adult' category one year- 3 were pre-bronze/bronze, 3 were gold- who do you think would medal? The 3 gold skaters refused to get on the ice until they made two events out of the adult event.)
My advice, which you probably don't need to hear if you've competed before: get there early. If you have a distance to drive, plan to get there really early. I've been in tears on the interstate stuck behind a truck pile up because I only gave myself 3 hours to get to a competition 1 hour away, and got there late. Also, plan to have things run late- that same competition was running so late the fact that I got there at my scheduled program time ended up making no difference! So be really flexible. You or your coach should watch who is on the ice. I put my dress on 1 hour before my scheduled program time (arrive in dress if I get there 1 hour early) and I put my skates on 3 skaters before my warm up, doing off ice warm ups about 7 skaters before my warm up (but I do really brief ones).
Just enjoy the experience and make sure to watch the other skaters. Cheer for your club, and they are more likely to cheer for you- though sometimes adult events are scheduled at lunch or end of day when other people have left
At least for me, I've never been at an overly competitive adult event- I've always talked with my competitors while waiting for warm up, and often while others in the group are on the ice. Just never when they are the next skater up! That's probably the big difference between standard track. You want to win, but most are there to have fun as a primary objective.
Good luck!