Seeing as Puerto Rico has it's own political parties, both of which have members that affiliate with the Democratic Party. Most politicians that affiliate with the Republican Party are members of the New Progressive Party. The other party, the Popular Democratic Party is mostl aligned with the Democratic Party. Since Puerto Rico has not participated in any national election, it is difficult to say which seats would fall to Democrats or Republicans if Puerto Rico was a state, but it's conceivable that Democrats could go 5-0, it really depends on local factors.
The best data available is from the 2004 Resident Commissioner race, where Luis Fortuno, who is affiliated with Republicans won a close race
From that map, we can gather that Fortuno probably won districts 2, 5 and maybe 3. This may not be a measure of what party strength would be, but it may be helpful data to study. It is clear each of the territorial parties has areas where there support is stronger, although of population density is any, Fortuno did win better in the less populated areas, typically something representative of Republican strength on the mainland.
It's possible that some of the districts could be wild cards based on local issues.
But, it all reality, we can't really know how the voting patterns would be unless statehood is approved, but it is fun to speculate.
I am ready to ready other posters thoughts on this and how they would draw a map.