When to Go
Puerto Rico is a tropical island, so temperatures don't vary much. When considering what time of year to visit, think about the "dry" and "rainy" seasons. Dry season runs from mid-December through mid-April. Hotel rates can be as much as 25% higher than the rest of the year, and hotels tend to be packed. This doesn't mean that rooms won't be available, but if you plan to beat that winter sleet in Duluth, make arrangements for flights and accommodations as far in advance as possible. A less expensive time to visit is during the "shoulder" seasons of fall and spring, when discount rates may be available, the weather is still perfect, and the tourist crush is less intense.
The best bargains are in the slower summer season, when temperatures are hotter, it's rainier, and hurricanes are a slim possibility. Puerto Rico can be an excellent hurricane-season option for the Caribbean for last-minute flight and hotel deals, when you'll be able to watch the weather report and know a storm isn't about to strike.
However, business travel—not to mention the fact that San Juan serves as a major hub for connecting flights to the rest of the Caribbean—keeps flights to Puerto Rico fairly full on weekdays all year long.