ASA is aware of the current dengue epidemic in Puerto Rico and is actively monitoring the situation. However, registrants should feel safe in traveling to the island, as there has been no indication to the contrary. The government-run Puerto Rican Tourism Company has issued an official statement (pdf) reassuring visitors to the island that the risk of contracting dengue remains minimal. Q&A about dengue fever (pdf)
Also, be aware that the incidence of hemorrhagic dengue, which is the more severe strain of the virus, is appearing in significantly smaller numbers than the other less devastating strain that results in flu-like symptoms. Nonetheless, it is important to take extra precautions to reduce this risk overall. Please see below for more information.
U.S. Center for Disease Control information on dengue (the CDC Dengue Branch devoted to the study of dengue is in actually in San Juan)
The above link includes a map that you can click on to get the most updated information regarding the incidence of dengue on the island.
Information regarding use of insect repellents: