I'm a little food centric and tend to plan excursions around where I want to eat. AS I was looking through notes and pictures of previous visits, I thought I'd add a post here.
In San Juan, we always try to stop at Metropol in Isla Verde for a quick lunch on our way from the airport. The black bean soup is very good. My dad always has to have some beans and rice and mofongo.
If we're staying in Isla Verde the night before an early flight out, we try to hit Ikebana in an unassuming shopping center above the Puebla Grocery store. (If you want Puerto Rican coffee, the Pueblo has a decent selection of coffee.) Ikebana has decent sushi with a tropical bent. The Fusion Roll with shrimp, crab, and salmon and topped with sweet plantain and mango was an interesting variation.
I always like looking at the stores that sell Vejigante Masks. The stores in Old San Juan are more expensive than in Ponce.
In Ponce, Kings Ice Cream on the central square serves some of the best ice cream I've ever eaten. They use 2 counter-mounted Italian gelato style mixers to make traditional and tropical ice cream. I ordered a mix of almond and coconut.
In Ponce, check out the Old Firehouse:
Between Ponce and Mayaguez on PR2 (really between Guayanilla and Yauco) is the La Guardarraya Restaurant that has been in operation for over 50 years. It is one of my Top Pork Spots in the World- pretty high honors! They serve a pork chop "Chuletas Can Can" which is a a full cut chop with a fried skin attached. Imagine a raelly good pork chop with a crunchy, puffed pork rind attached. Make sure you order a side of fried plantains and rice and beans!