The white-sand beaches of the Caribbean have been the backdrop to many a honeymoon, anniversary, birthday, or “just-because” romantic trip. But with thousands of islands and cays in the region, some travelers might find it daunting to pick the perfect destination. To help you choose, we've narrowed it down to the 15 best Caribbean islands for a couples getaway, paying special attention to the most romantic hotels and restaurants on each. Whatever your priority—spectacular scenery, a private beach, an in-suite pool, or adventurous excursions—these are the most romantic Caribbean vacations for couples. Grenada Getty Images/AWL Images RM Grenada has idyllic sands, tropical trees laden with fruit, a dramatic coastline, and the constant smell of nutmeg in the air.…