Actually, April is a great time to cruise, lower humidity than in the summer/fall, plus its not hurricane season in April. Its still plenty warm in the Caribbean, although the temps don't vary much there anyway.
Donna and Rosetatto are right on the button. The western Caribbean enjoys the trade winds directly out of the east, across the sea, so it's nice, warm, with low humidity in direct sunlight, and pretty cool in shaded areas. Hit it!!!