Liberia is the other door
Daniel Oduber International (LIR) in Guanacaste serves the north-west beaches. If your trip is Tamarindo and Nicoya only, it saves a long transfer.
Domestic hops and shuttles
Sansa flies from San José to Quepos, Tamarindo, Drake Bay, Tortuguero, Nosara, Tambor, Cóbano, La Fortuna, Limón and Golfito. Tourist shuttle vans are the road alternative.