http://www.sazonboricua.com/
Where she posts recipes of great puertorican dishes. In her last post she covers some of the street/beach/neighborhood food a lot of us grew up with. I took my kids over xmas and we hit some of the highlights.

That would be the ubiquitous sign that precludes running a tab.
One of the great street foods in PR are pinchos, which are seasoned pork or beef skewers cooked over charcoal and served with bread and a beer.

These were awesome


Another great place to eat in PR towns is in the local panaderia or bread/pastry/deli

where you can go for a sandwich or more fancy fair, such as white asparagus

Flan

or octopus salad

Along the beach in Luquillo there are some very well known stops for a quick or not so quick meal. We sampled a few such as pionono
(plantain stuffed with beef)

Lobster empanada

alcapurrias (see Jeannette's post for recipe)

and empanadilla (empanada) of chapin (which is a coral reef fish)

Please check out the Sazon Boricua post for excellent recipes.