If you are planning on staying longer on the island to explore or vacation, I recommend visiting El Yunque National Forest. Due to COVID restrictions, you now need to make a reservation to visit La Mina Falls. Dates/times are only available 30 days in advance so be sure to plan ahead so that you're able to visit! More info: https://www.fs.usda.gov/detail/elyunque/passes-permits/recreation/?cid=fseprd716216
I highly recommend booking a Catamaran for those of you who enjoy sailing, swimming, or snorkeling. If you don't have a rental car to drive to Fajardo, several of these companies also offer shuttles from the San Juan area. They take you to the deserted island of Icacos and Palominitos Keys, serving food and drinks all day. Here are a few companies to inquire with: Salty Dog, Spread Eagle, East Island Excursions, Traveler Catamaran.
If you're interested in visiting some of Puerto Rico's smaller islands like Vieques or Culebra. Both islands are gorgeous! Nick and I went to Vieques most recently and enjoyed seeing their wild horses, clear waters, bioluminescent kayaking tour, and black sand beach.
This place offers guided ATV and horseback riding tours with short narrated breaks where you learn more about the history of the Puerto Rican countryside. Enjoy an onsite Mojito Bar afterwards.
ATV, UTV, and Horseback Riding adventures, along with an onsite Go-Kart track and restaurant. Be sure to book online ahead of time because they can sell-out.
I highly recommend exploring Viejo San Juan. It's both historic and scenic. There are tons of shops and restaurants to enjoy while you take in all the ocean views or in-between seeing historical landmarks.
Castillo San Felipe del Morro, also known as El Morro, is a citadel built between 16th and 18th centuries in San Juan, Puerto Rico. Countries fought for control of this tiny yet strategic island for centuries, and this National Historic Site was used by the Spanish through several attacks by England from the 1500's to the 1700's, until it was conquered by the US in the Spanish-American War in 1898, then used as a US Military Base through both World Wars.