Where to stay: Jaco is Costa Rica's nightlife hub; try Morgan's Cove Resort and Casino or the Best Western Jaco Beach Resort, which are both near clubs, restaurants, and activities.
Where to party: The Monkey Bar is a great first stop for your night of partying (one TripAdvisor reviewer calls it "college life, without the college"). Next, hit up Le Loft for the kind of booze-and-fun-filled night on the town that makes a vacation memorable.
What to pack: Sunscreen (the rays are strong here!) and sneakers and clothing for daytime adventures like zip lining and experiencing the country's "Pura Vida."
When to go: Late December through April, the country's dry season and the best time for rain-free sun.