I have been waiting to see what others tell you but since a few days have passed, I'll tell you what someone told me. First let me qualify this by saying I have no idea if she knows what she's talking about, and my impression is that she's not the most reliable source, but she is a teacher at Dominico, so maybe there's something to what she says. She told me that she checked into becoming a certified translator but that you need to be a native born DR citizen (or maybe just a citizen), and that certifications aren't being given out right now because there are too many in circulation. Furthermore, the people who have the certifications "bought them" and are not very good at their craft, go figure. My wife tells me that La Cancilleria is the place to find out.
Disclaimer: Can't vouch for any of the above info, maybe other posters can help us on this one.