Travelers must pass through customs at the airport in Puerto Rico [1] before leaving the island to make sure no prohibited plants or fruits are taken off the island. Permitted items include avocados, coconuts, papayas, and plantains. Mangoes, passion fruits, and plants potted in soil are not permitted. Pre-Columbian items or items from Afghanistan, Cuba, Iran, Iraq, Libya, Serbia, Montenegro, and Sudan may not be brought into the United States. There are no customs duties on items brought into the United States from Puerto Rico.
Links:
[1] http://www.moon.com/destinations/puerto-rico