We've eaten there twice. Both times DH wore an oxford shirt, no tie, and slacks. I think he's had a sport coat with him both times as well, not that it's required but because he felt chilly. I wore a linen pants suit one time and a summery dress the other.
Most seem to wear anything from business casual to semi-formal (they get some weddings). We've seen one party in shorts and t-shirts, they were pretty sweaty and manky and had obviously come right from a theme park. They seemed very out of place with the atmosphere there.
Anne