I'm
posting this from a cafe in St. Martin on the French side where I'd run out of Euros and paid in US$ not more than 10 minutes ago
As mentioned earlier in this thread, many restaurants offer 1:1 so that they can compete against the cheaper pricing on the Dutch side.
The Dutch side officially uses the NAF but I've never seen anyone actually use them, the US$ is accepted.
St. Barths was euros only, but I admit that I never tried to pay in US$ and I'm sure that they take them.