Many of these people are already evacuating the island. Avoiding the rush is a very smart thing. When it is neccesary for people to evacuate, the water taxi does not charge a fee or charges very little. The airlines also cuts their rates by about 90% in the event the island needs to be evacuated. I remember for Wilma, there was a line up at tropic air all the way down to Monchos.
Thankfully, we are not at this stage yet and all the computer models now show it going north http://www.weatherunderground.com/tropical/tracking/at200704_model.html. but still too soon to let our guard down.