Just got back from AC. The Trade Winds keep the mosquitos in check - if you are on the beachfront. They're not a problem during the day.

We burned a mosquito coil in our bedroom and bathroom a couple of times. They work well. Also, leave doors and windows open during the day for the breeze, but close everything that doesn't have a screen as evening approaches.

I, too, had heard about sand flies, but we didn't have any trouble with them. We didn't take Malaria medication since we spent most of our time on the island. Inland is probably a different story. The lagoon side of AC probably has a lot more mosquitos than the ocean side.

Use an insect repellent with DEET and make sure that you use it when you go out in the evening.

If you're going to spend much time inland, Malaria medication might be adviseable - but check first - I've heard some people have nasty side effects - you'd hate to be sick on your vacation.

Good luck and enjoy your trip!