Once is bad luck,
Twice is coincidence,
Three times is enemy action.
Actually I’m for the forcing of PR to either be a State or go Independent; with the sole exception of DC the Federal government is supposed to be comprised of individual STATES. {Commonwealths fit the description.} The reason DC was not to be in any state was so that no state would have disproportionate control of the seat of the federal government; naturally granting DC statehood {and even Senators} would be a violation of that idea...
Representatives, not so much; the revolutionary war was, in part, due to taxation without representation, and it can therefore be reasoned that any people taxed should have its representatives in federal government. However they are not, strictly speaking, needed for even DC; DC could be zoned such that there are no residences therein and therefore has no population to represent and it would be more of a place where various federal functions take place than a city.
As for Puerto Rico, it's a tar baby. We can't let it go, lest it get taken over by someone like Castro or Chavez, and we can't make it a state, because it really doesn't fit with the rest of American culture. We'd be stuck with a permanent problem like the Canadians are with Quebec.