You are going to lose 15-20% swapping out DOP outside RD in a cambio @ home, either save them for another trip, or make a "private" arrangement with someone traveling from there. Be patient and you are better off waiting for a helpful traveler. What is a "lotta" DOP?
I agree with this. I looked into this a long while ago, and the currency (for obvious reasons) is not really a wanted currency outside, so just as said, the rates are bad. If you are already out of the country, I would try this "exchange" Tamborista mentioned, or just save it, bearing in mind the slight inflation there might be...
I would suggest always leaving the country with as little DOP as possible, but not exchanging at the airport though if not possible earlier.