Young Man,
my vote hands down is - Boca Chica!!!
It's great fun - both risque and serene. It's what you make of it. ANd, very close to the fun capital of Santo Domingo.
When I go to the RD, being both an avid beach bum, AND an avid party man, I go to Punta Cana for the caribbean's best beach, and to Boca Chica/Santo Domingo for great fun & culture.
For Boca Chica, Check out the Costalunga Residence Club, 2 blocks from the beach, relatively modern and new. I understand that this is one of the most comfortable non-all-inclusive accommodations in the area right now.
www.costalunga.net
Enjoy yourself bro!