Yes that is true. Resort workers that work in the Playa Dorado complex in Puerto Plata could get into Mangus on Tuesday nights for free and drink beer or rum for free until 12:00, I think it was. They always thought I worked for Coco Tours and I never paid to get in any night and also had free Presidente on Tuesdays.
I know they get a "drink card" for Roadway and Coco Bongo that is good for 2 drinks a night.
I'm assuming they have something similar in Punta Cana also.