I'm sorry, that was meant to read "no local food or water" which is what the OP says.
I can't imagine 3.4 million people stick around with no electricity for 4-6 months, and no local economy. I did not at all mean to claim 3.4 million people have left already.
I am guessing if the electrical grid is truly destroyed and will take 4-6 months to rebuild as reported, how could that not lead to a mass exodus?
A lot of people will leave (and a lot of people have been leaving because the economy's been in freefall and they've been imposing more and more extreme austerity measures to keep paying bonds), but the island will not by any stretch of the imagination be deserted.
Hyperbole, noun: Obvious and intentional exaggeration; an extravagant statement or figure of speech not intended to be taken literally, as “to wait an eternity.”
Surely there are still 3.4 million Puerto Ricans on the island?
Are they all starving and without water?
Might you possibly be exaggerating?