I usually pay cash for things in SXM except rental car or significant jewelry - simply because I prefer not to use cc on island that much. I often bring some euros to SXM when I know that I will be paying operators/vendors who do not adjust their exchange rate to market and use a rate which is higher than market - such as 1 euro to 1.3 dollars. Some will also give you a better price if you pay in cash - any kind of cash - if you want to ask or bargain about it.