Your sentiments are well understood, however you completely ignore the original reason for putting the lights in in the first place.
The spat of muggings that have occurred on that dark unlit road at night have forced the issue. The road north needs to be lit to protect the increasing number of people that are traveling north and the people that already live there. There are plenty of underdeveloped places with low growth forecast to retire to. Ambergris Caye is not one of them. The island has changed dramatically in the last ten years and will continue to change as rapidly if not faster in the future. Its just how it is.