PR probably won't since it will be a swing state, and I don't think both parties have interests with that.
There's approximately a 0% chance PR is anything but a solid blue state if it were to ever to be admitted.
Puerto Rico's current Rep is actually a Republican. I think it would vote like the Cuban districts in South Florida.
Yeah, PR is pretty socially conservative, so - as their non-voting representatives have exemplified - good GOP performances are definitely possible (though probably less so when the federal government under GOP control has basically refused to assist the island, be it in the aftermath of its debt crisis or - barring the President doing nothing more than throw some rolls of paper towels at people - a devastating hurricane).
I think you are forgetting about the fact that PR has a completely separate party system. Now, the pro-status quo party representatives, if any get elected, have a 100% chance of being Dems (assuming the party does not collapse in the process of course), as they are also the more left wing of the 2.
However, the pro-statehood party tends to alternate between supporting Democrats and Republicans in the mainland, probably as a way to show that PR statehood will not bring a partisan advantage to either side. I imagine this party will actually side more often with the Republicans than with Democrats if PR gets admitted as a state. So PR, at least in terms of representation in Congress (where their regional parties will compete), will be a swing state of sorts, though I expect any PR Republicans to be called RINOs and be incredibly moderate.
As for the presidency, PR would indeed be a safe state though, probably giving Dems around 70% of the vote.
Of course that arrangement is also quite an unstable one and I wonder for how long it would last before PR votes on generic Dem vs Rep lines like everyone else
