What if I want some vegetarian and some meat meals?

You have to sign up for one or the other. BUT, at the end of the meal, after everyone has been served, it's OK to go through the line again to sample the veggie food if you signed up as an omnivore, or vice versa, if there's extra left. "After everyone has been served" are the key words here, like wait at least half an hour after meal time began.