I have lived in Puerto Rico for over 40 years, and call myself a "Gringorican". But i am not really quite an expat because Puerto Rico is a possession of the US. This means that all persons born in Puerto Rico are automatically US Citizens, and there is no restriction of travel from PR to the US.
However, any US citizen living in PR automatically becomes a second class citizen - which is not supposed to happen - because we can not vote for President or Vice President, and we do not have a full member in either House or Senate. What we have is a non-voting member of Congress who can serve on committees. We also get to participate in the nominating process, and get to vote for the candidate - but we can't vote in the actual election.
(Moderated: no political opinion on the forum pls)
So everybody living in PR is sort of an expat, but not quite. Just second class citizens until we move to a state. Then our status is instantly upgraded to full citizen.