Definitely pick up Bruce Van Sant's "The Gentleman's Guide to Passages South" for the Mona Passage
. It can be a bumpy ride across, and you will want the local knowledge for the crossing.
Beyond the obvious stuff like Vieques, here are a few suggestions:
Caja de Muertos is an island off the south coast of Puerto Rico
near Ponce. It's worth a stop. You will likely be the only vessel there. It's a protected nature reserve, and the snorkeling is nice. If you walk around the island, you'll find a lot of smaller wildlife. There is a lighthouse to check out, and some heavily overgrown paths to hike as well.
Monkey Island off the east coast
of Puerto Rico
is also worth a sail-by, but you can't go on the island itself. You don't need to, the monkeys will show up along the shore and start yelling at you and throwing things. It's pretty funny
as long as you stay a safe distance away.
If you get up to Ponce, there is an ice cream place across from the fire station that has a bunch of interesting flavors. Definitely worth a stop.
If you have access to a car on Puerto Rico, make sure to head
directly to Guavate up in the mountains of the southeast part of the island and eat a bunch of lechon.