I've been to Curacao a bunch of times, usually very few bugs, but a couple times they've been a real pain. I'm not sure how to predict. I think if it's been raining there will be more. If you've got wind it will help keep them away, usually you do but some times of year it dies down. Curacao is still a fairly dry desert island compared to most of the Carribean, but it seems to be the wettest of the ABCs. It's the largest and has a little more elevation to catch weather, especially at the western end.
Depends where you are too. I was just there in August. We stayed at Lodge Kura Hulanda and there were a fair number of bugs, I'm guessing because they have a lot of irrigated landscaping. We stayed at Habitat for the rest of the trip, it was less of a problem I'm guessing because it's more of a desert landscape, though they can still be a big nuisance in the open air restaurant. Didn't have a problem around town even in outdoor restaurants, which is many of them. I particularly remember bugs being a problem on another trip we did to Habitat that was July/August.
I don't recall bugs ever being a problem in Bonaire (or Aruba), but it's been awhile since I've been there.