I always go to Patio the Sam
I visit Old San Juan every year to visit friends and family. El Patio de Sam is a must for a nice lunch or early dinner after spending time visiting Old San Juan. My preference: Chicharrones de pollo con tostones (crunchy fried chicken with green fried plaintains), and a local beer of course. The food is excellent, the service too but what I liked the most is the ambiance on this indoor "garden like" dinning area.
Location is fabulous, just a few steps from El Morro fortress and close to indoor government parking lot.