Yes, I've heard of a marketing and sales executive association and an Association of Advertising agencies, and there's probably a couple more. You might want to contact the U.S Embassy here in the D.R. to help you contact them and provide you with other services. They have a very complete web site at:
http://www.usemb.gov.do/indexsp.htm
also you might want to contact the local American Chamber of Commerce at:
http://www.amcham.org.do/
GOOD LUCK