A favorite with the locals, especially government workers at lunch, this place is always packed, and with good reason. For $10 or less for an authentic and delicious lunch special (with a drink), this place is a steal.
Try the asopao de camarones (shrimp soup with vegetables and saffron rice) with a side of tostones (mashed and fried plantains) and ask for the local hot sauce, pique, a smoking mixture of habañero peppers, black peppercorns, spices, and oil and vinegar.
Service is reasonably fast and the waiters are friendly, but certain times of day (12-1pm weekdays, and 6-8pm on weekends) can be impossible for getting a table. Reserve ahead, or be prepared to wait in the plaza nearby.