Thinking about a vacation to Isla Mujeres next winter. What I've read about it's slightly out-of-the-way, low-key nature appeals to me. But I've also read about tour boats that bring tourists over from Cancun. So the question is, do the tour boats from Cancun adversely effect the ambiance on Isla Mujeres? I have no desire to be surrounded by throngs of day trippers from Cancun, and all that that implies.