There are 78 municipalities in Puerto Rico.
Names from CIA World Factbook (http://www.cia.gov/cia/publications/factbook/geos/rq)
... the town the population is spread out with 25.2% under the age of 18, 4.8% from 18 to 24, 27.3% from 25 to 44, 28.7% from 45 to 64, and 13.9% who are 65 years of age ...