November to February means high season and high prices; cyclones are possible from January. Accommodation and air tickets can be hard to come by, so book well in advance if travelling at this time.
October, March and April are still considered high season in places, but there are generally fewer crowds. Underwater visibility is especially good for diving and snorkelling at this time. All in all, it's a nice time to be on the island.
Lower prices and milder temperatures arrive from May to September, when there's little chance of cyclones.