Disney works very hard at mosquito control. In fact, many of us believe the filling in of the old River Country pool in the last few months was part of that program, as a primary effort is to reduce or eliminate bodies of standing water where the little monsters breed. There is also an active program of natural control through plants and animals, and I believe a pesticide based program as well. It is incredibly rare that I have ever come across a mosquito in the parks or on hotel grounds. However, The Fort definitely has more mosquitos than most areas, even if it is a pretty low number for a Florida campground. Like everywhere else, it is worse in the summer. For example, we didn't see a single mosquito our last trip, but it was in December, while the trip before, in September, my family of 5 picked up about 4 bites total over a week. To be fair, one may have been an ant.
Regardless, there isn't a problem per se, but there definitely are mosquitos. Just not very many, especially for FL. Disney has been handing out bug spray at check in to help as well.