Hi Ray,
Most of these paintings that you see either at the resorts or the Malecon, are of Haitian origin. They are sometimes referred to as naive (sp?) art. I have picked up two of these. They are so easily spotted too. I don't know of any web sites, but next time you go back to the DR, I suggest a trip to Sto. Dgo. There, you will find immense variety of art works by famed Dominican artists, and up and coming too.
As a side note, the National Press Club of Wash. DC in conjuction with the Smithsonian Inst. had the works of three famed Dominican painters: Candido Bido', Dionisio Blanco, and Guillo Perez until Oct. The majority of the prints sold out, and several originals sold for as much as US$13,000 a piece. I couldn't even afford to purchase a signed print :-( My dream is to have an original by Bido'.
Regards,
Natasha