Your day not theirs, wear what you want, you chose them not vice versa.
I went in casual clobber and asked all sorts. Will you feel happy there? Is it worth it? What are the facilities like in comparison to elsewhere? Do you feel like you'll be listened to? Can they adapt to your learning requirements? Do the costs include fees? How much is accomodation? What is the first time IR pass rate? How much is additional training? How long will you be in america for? How much is the on site gym? How many people will be on the course? Will i get a nice discount on a TR if I'm prepeared to pay for it? Can you go and have a look at an aircraft? When can you go and observe a sim? Are there any other students around to speak to?
The list goes on. Its all about you.
Enjoy.
CR