Surely there are public health issues here? After all dogs aren't allowed in food shops etc etc. I don't know if Lemurs cover their feet and hands with their own urine like squirrel monkeys do but it still sounds like a health hazard having them running around near food, quite apart from any actual aggressive actions.
The food areas are away from the 'free ranging' lemur areas, seperated by gates, which amusingly say 'don't let the monkeys out'. However, on all my visits there has been the odd ringtail or two around by the cafe and entrance.
The thought of a cafe being within the free ranging area would be chaos, and incidents like the one reported would probably be occurring daily!