I went to Puerto Rico last year. Vieques and nearby Culebra islands are quite beautiful, sporting (in my opinion) best beaches in Puerto Rico. Powdery white sandy beaches, pristine water. Culebra is better of the two in my opinion, particularly given toxic chemicals from all the weapon tests US Navy performed several years ago.
If I were to fault the area, it would be isolation (which you may want, especially given the amount of cars in main island). Nearby Fajardo offers a lot accommodation, but that requires a ferry ride, which isn't cheap and convenient. If you want easier access to places like Old San Juan and El Yunque rainforest, it may be better to get a place in Fajardo instead. If you don't, Vieques is quite nice.
I found bioluminescent waters to be quite overrated. The water does glow when you splash into it (e.g., kayak peddle), but the effect is very subtle at best.
My three favorites from Puerto Rico: fantastic food (especially mufungo), El Yunque, and great beaches in Culebra. Old San Juan gets an honorable mention. 3 least favorites: lots and lots of cars, feels a bit too familiar (too US-like), lame for snorkeling/SCUBA.
I didn't see any poor children on the street, although parts of downtown San Juan can be scary (cops carry big guns there). But overall, I found Puerto Rico to be quite safe (particularly to the east) and locals are highly educated (and many speak English fluently) and hard working.