If they have become a citizen of PR and aren't solely there on vacation (I believe the laws that define state citizenship themselves vary state-by-state), yes, they can't vote in federal elections. There are still local and territory-wide elections they can vote in.

This is silly, yes. The answer is making PR a state, but historically they haven't wanted to be one and Washington has been hesitant to make them one. Here is a short video on the matter which coincidentally was published a few days ago: https://www.youtube.com/watch?v=Mk6JrUYLyWw