If you are looking for authentic Caribbean food, the UWS (as usually defined) is not the place to go. Rather trek out to Crown Heights and other parts of Caribbean Brooklyn. One place that I liked a lot was
Cock's, which is a Bajan restaurant (I posted about it on LTH).
In Harlem, there are several Guyanese restaurants, and many in the Richmond Hill area of Queens and Morris Heights in the Bronx. But, of course, on the UWS there will be Caribbean restaurants, but tamed and upscale.
From the NYT in 2007 (haven't eaten there myself, but it is Manhattan):
SISTERS CUISINE +
(212) 410-3000; 1931 Madison Avenue, at 123d Street; $; no smoking; American Express, Mastercard, Visa; breakfast, lunch and dinner daily; no pork, no alcohol.
Marlyn Rogers and her sister Elsie Darrell have infused their food with the flavor of Guyana, their homeland. The restaurant balances healthful fare like calaloo (a combination of okra, spinach, cream of coconut and spices) with traditional Caribbean and Southern dishes like spicy Jamaican jerk chicken, oxtail stew, curried goat and sauteed codfish. Side dishes include fried plantain and Guyanese meat patty; among the desserts are pineapple tart, sweet potato pie and peach cobbler. Everything on the menu is under $7. ($25 and Under: 8/25/95)