score:2
No, you can't use PR. As you already know, PR is a U.S. territory, so in terms of immigration it's the same as Florida or Alabama, i.e. the immigration doesn't care. Flights to PR from the mainland are domestic flights, and vice versa.
You MUST go to another country that is outside U.S. borders. The Bahamas, Mexico, Canada or some other Carribean island could work.