A very nice naval base at Samana Bay, Baez gets to be president for a little while longer, and the first black majority state.
The other thing is that the US is probably going to have a softer hand than Spain did and administer it more like a territory than a state at first while looking to integrate the people into the US slowly. There's probably going to be at least one revolt on the island (which depending on American actions may or may not succeed) which might be how Baez gets the boot.
I could personally see a number of freedmen going there to try and start anew which would help with the Americanization of the place. But I can't see statehood coming before 1885 at the earliest, more likely around 1890.