Provision in SXM, it's cheaper than St. Bart's or Anguilla. Plan on having a bit of a limited selection of meats compared to the US, but all in all not bad. Be mindful in pricing your
beer that the Heinekens are the small bottles, so even though you pay $.50 a
beer, you lose out on the baby beer. Taxis are zoned and you'll get dinged for stopping, so definitely rent a car. You'll pay less than $50 a day.
If you're into it, stop at the Royal Marche over the bridge just south of Marigot. There you'll find all sorts of French meat pies, sandwiches, wine and the like.
If yo find yourself having to pick up items in Anguilla, avoid Lakes in The Valley in favor of Procters.
Price and selection are much better.