Autoridad Metropolitana de Autobuses (787/250-6064 or 787/294-0500, ext. 514, www.dtop.gov.pr/ama/mapaindex.htm [1]) is an excellent public bus system that serves the entire metropolitan San Juan [2] area until about 9 p.m. It’s serviced by large, air-conditioned vehicles with wheelchair access, and the cost is typically a low $0.75 per fare (exact change required). Bus stops are clearly marked along the routes with green signs that say “Parada,” except in Old San Juan [3], where you have to catch the bus at Covadonga Bus and Trolley Terminal, the large terminal near the cruise-ship piers at the corner of Calle la Marina and Calle J. A. Corretjer. When waiting for a bus at a Parada, it is necessary to wave at the driver to get him to stop.
Links:
[1] http://www.dtop.gov.pr/ama/mapaindex.htm
[2] http://www.moon.com/destinations/puerto-rico/san-juan
[3] http://www.moon.com/destinations/puerto-rico/san-juan/sights/old-san-juan