Hi, Schuttzie. As James38 states, residents of PR cannot vote for President. However, if you never establish residency in PR and maintain your residency in whatever state you spend the rest of the year in, then you can vote through that state. Bottom line: Count the days to make sure you don't establish residency if voting in US elections is important to you.
I respectfully disagree with James38 that the Constitution should be amended to remove the Electoral College. Without the EC, a vote for President from the jurisdiction of PR would be equally worthless as candidates would only concentrate on a handful of the biggest states by population (and even then, really just the biggest TV markets in the most populated states). Candidates would only campaign in NYC, LA, Chicago, TX, CA, FL, etc., As it stands now with the EC, it's still possible for your vote to count in tightly contested states like NC, VA, NH, FL, CO, etc. With the exception of FL, if there were no EC, all of these states would be completely ignored by presidential candidates.
All that said, if PR became an independent country as James 38 advocates, then James would have the right to vote as a US citizen in a foreign country! This is because US citizens resident in foreign countries can vote for President (but no other offices) through the state to which they have some connection (even if they've never actually lived there). Such is the case with Americans in Ireland, many of whom I have helped to register to vote for presidential elections.