The US no longer needs Puerto Rico. It has no strategic value with modern warfare, which is why we "needed" it originally.
Most Puerto Ricans don't seem to like the US much, even the ones living in the US.
I have also found that to be true. But I don't quite understand it. I took a look at the streets of Puerto Rico with Google Maps. It is.. a DUMP. Just about every state has it's good and bad parts. I could find no good parts in Puerto Rico other than the parts with no people living there. It has some beautiful mountains, etc.
As for the developed parts.. it is all quite run down, and doesn't have many stores of any significance. The only buildings worth a damn are the hotels.
I bet they have very lax drug laws. Not many drug addicts would like to fall under federal jurisdiction.