I don't know if you came over or not, but if you still have time and money to try this: (posted by me in opencarry.com)
Under Puerto Rico law there is no reciprocity for out of state citizens to posses/carry firearms - even if that citizen holds a fireams license/permit from a jurisdiction other than Puerto Rico.
However, any US citizen can apply for a Puerto Rico firearms license, regardless of the citizen's state of residence - 25 LPRA 456a
(I doubt that anyone has done this before, as doing it would be an extremely tedious process, but theoretically it can be done). This license will allow you to posses up to two firearms in your domicile
(where you plan to spend the night) and up to 50 rounds per firearm. You are not limited to the number of firearms you can posses in your domicile
with a shooting permit - 25 LPRA 457c
. A temporary shooting permit is also available - 25 LPRA 457d
(an example of the petition for the permit can be viewed here
Upon obaining a Puerto Rico firearms license, that citizen can petition a Puerto Rico court for a permit to carry firearms in a concealed manner on any jurisdiction of Puerto Rico - 25 LPRA 456d
. The thing is that you need to prove to the court that you fear for your safety while you are in Puerto Rico. Heres where you'll have to get creative when you articulate your need for a firearm while you stay in Puerto Rico - an example could be that you fear for your safety should you be selected by a criminal for a carjacking, an ATM robbery, etc.
Disclaimer, I'm not an attorney, just reading off the statutes.
Hope it helps.
Link to Michie's Legal Resources for Puerto Rico - Puerto Rico Arms Act of 2000
Link to post in opencarry.com: