They don't have like somalian gun boats but the fact is... there are pirates in all waters. Your pretty safe as long as you book your excursions with the cruise ship DO NOT TRUST ANY LOCALS. I wouldn't eat any food from the locals either unless have a tough stomach.
I've been to D.R many times traveling from north to south.. its a very hard life on that island with a lot of desperation. If you choose to travel around be prepared to see some stuff you won't ever forget.
On a lighter note I bet that area hasn't been MDed much so you stand a good chance of finding some goodies.