We too had dinner at American Dinner on Sunday. We had a sandwich and filet with fries. The sandwich was just ok, advertised as a panini but didn't look close to anything I have had before with the name "panini" by it (not pressed). The filet was pretty good (probably around 6oz) especially for the price (360 ITBIS included), a bottle of sparkling water and a cuba libre. Total bill was RD$670 (without tip). Decor also nice, although I found the bench seats too high or the tables too low, hard to sit there comfortably. Service was okay, no complaints. The fries (which I ate because I was really hungry) were fried in a very low quality oil; an aftertaste of something I couldn't well figure out what it was. Definitely will not have fries there again.
There are so many places to eat in Cabarete (and I hear a few more coming up) that unless you have great food, affordable prices and top-notch service, I don't see how this American/Belgian sort of diner will survive.