There are 9 threads you can read on HIV,aids and testing of resort workers at the bottom of this post
Important info if you're in a relationship with a Dominican
Don't be fooled into any false belief that they are safe to have unprotected sex with. There's a 3 month window after contracting the virus before it shows up in a blood test.
I've heard that when they are hired some hotels will do all the testing, mostly to protect themselves from having sick employees and after that they would be tested for things that can easily be spread in food handling like hepatitis or TB.
They certainly don't do it for the protection the tourist who have sex with them.