From San Juan there is a coastal road that goes east and eventually winds up at the town of Loíza, which is known for its Afro-Puerto Rican traditions. One of the best known of these is the feast of Santiago Apóstol (St. James the Apostle), that takes place at the end of July. There are various religious practices that take place during this feast, such as prayers and a parade that features masks and costumes called vejigantes and the performance of an African-inspired dance and music tradition called the bomba.
Back in 1984, when I first visited Loíza, the road from San Juan was a narrow lane of asphalt that ended at the river with a hand-pulled ferry. The ropes extended across the Loíza River and the workers pulled furiously at them to move the metal ferryboat across the river. Since that time the road from San Juan to Loíza has been widened to two well-marked lanes and the metal ferryboat, known as an ancón, has been retired and replaced by a bridge.
See my webpage on Puerto Rico at http://www.latinandcaribbeantravel.com/puertorico.html