Can I eat before class? I've heard you shouldn't.

It's better to come not on a full stomach - about an hour before class is too late for a heavy meal. The reason is simple: the practice includes hangs and inverted positions, and that's uncomfortable on a full stomach. A light snack in advance is fine, there's no need to torture yourself with hunger. If you're unsure, have some water and tell the trainer how you're feeling.