A general comment; When I have gone to a restaurant that I am not at all familiar with, that is without menus (or a menu board showing prices), I will ask the prices. Similar to the idea of getting in to a taxi in Jamaica, you want to know the deal before the ride.
Of course any establishment that would take advantage of unsuspecting clients will not be around for long anyway. As another boardie noted, there are far too many great options for food in Negril.