How would that work? He’d have to move to the mainland to be able to vote for himself, wouldn’t he? It is my understanding that PRs are US citizens, but they can vote only if they live in the US.
You are correct. While residing in Puerto Rico, Puerto Ricans cannot vote in U.S. presidential elections, but they can vote in primaries. Puerto Ricans who become residents of a U.S. state can vote in presidential elections.