If you want to know dominican people, when I was last May in Playa Real, all the weekends lots of dominicans came to the resort to spend their weekend, but when I was in Decameron (last December) they were some, also.
About discos, I agree with Katia. Outside resorts, you can try BOULEVARD bar, just opposite Playa Real where many people who works in the resorts go at night. Also Chocolate Bar (near Decameron) is good (of course they are bars, not discos).
And I recommend you BAR LA CANITA, in front of Melia Juan Dolio.
The managers, Patrick and Dominique, are french, and are really nice people. Some nights the atmosphere is almost like a disco...
Don't doubt to email me if you need more info.