Day trip (<1 hour drive from the city) Cahuita/ Cahuita National Park - Cahuita is a village near the border with Panama. It's a gateway to Cahuita National Park famous for its coral reefs and the rainforest that is home to toucans, monkeys and turtles. You can also visit the black-sand beach of Playa Negra in the north of the village, known for its strong waves. Farther north, there is a Sloth Sanctuary that cares for injured sloths.
The Bribri Talamanca Indigenous Territory Reserve - this is one of the four Costa Rican indigenous territories of the Bribri ethnic group.
Gandoca-Manzanillo Refuge - Sprawling preserve with beaches & wetlands, protecting a vast coral reef & mangrove oyster beds.
Weekend Trip (>1 hour drive from the city) Bocas del Toro, Panama - Although Boca del Toro is in Panama, it's very close to Puerto Viejo. It is a gorgeous archipelago where you can snorkel and watch dolphins swim.
Surf is the most popular sport in Puerto Viejo, you can find professionals from all over the world coming to town to ride the waves at Salsa Brava.