We rented a house in St. Lucia for a week back in '96.
From what I remember, there wasn't much of a bug problem at all. It can be quite warm in the evenings, and the house we rented did not have A/C, but with the ceiling fans on and the windows open we were comfortable.
We stayed on Marigot Bay in a house called the Marigot Round. Do a search. It was a tremendous piece of architecture. We hired a private boat to take us around the island for a day tour and stopped at anse chastanet for a drink or two. The resort and beaches are beautiful there. If you dive, it is paradise. Nice choice!