Cahuita village is genuinely walkable — you can cross it in ten minutes on foot. The main street, the park entrance at Kelly Creek, the beach, and most restaurants are all within easy reach without transport. The unhurried pace makes walking pleasant rather than merely practical.
For longer distances, bicycle rental is the sensible choice. Bikes can be rented from several places in town and are particularly useful for reaching Playa Negra to the north and the Puerto Vargas park entrance to the south. Taxis are available and reasonably priced for the 12 km trip to Puerto Viejo de Talamanca — agree on a fare before getting in. Alternatively, local buses on the Puerto Limón–Puerto Viejo route pass through Cahuita regularly and make the connection cheaply.