Going in October. Do the temps get chilly at all? Should I pack a sweater or anything? Never been in the Caribbean other than a cruise and def needed sweaters cause the ships were cold.
In October, the average daily maximum is 30° C., and the average overnight minimum is 23° C. With an average humidity of about 75%, it feels hotter. That minimum temp is recorded around 4am, so it's still warm in the evenings.
In the past few years, I've never even needed long sleeves in the cooler months (Dec. to Feb.).
You might want long sleeves for protection from the sun or insects, or on boat trips when it might be breezy.
I was there in December and January and never needed long sleeves. My wife gets colder than I do and sometimes wore a long sleeve shirt at night if we were sitting out by the water.