I have been there for vacation and for work. The rain forrest is beautiful and that part of the island is very beautiful. But PR has a high crime rate. Even in the day time when in San Juan be on guard of your valuables. Do not wear you jewlery to PR... its one way the criminal element targets individuals , based on the jewlery they are wearing.
I have been there various times, once on a cruise ship stop. The cruise advised those going into San Juan not to wear jewelry and stick to main streets. When I was there for business purposes , the hotel advised us not to "go to town" after dark.
Resort areas and higher priced hotels do their best to provide additional security on their property and you can be quite safe at those locations.