Sara, I would go for mix-and-match colors (mostly black with a couple of bright shirts, ideally ones that match every one of the pants/skirts you bring).
Leather shoes are best--I would do sandals if the weather cooperates, or otherwise comfortable Clark's or Born-style shoes. Again, something that matches all your clothes!
And you'll look American no matter what you do, so just try to be comfortable and wear things that you won't be embarrassed to see in photographs 20 years from now.
Tara