Milka's Grocery on the canal between Ensenada Honda and the ferry dock, with a dinghy dock. There are a couple of other options, but they have a meat counter with good lean beef. I would skip Fajardo, but they have big box stores and our favorite Ralph's Food Warehouse.

On Vieques in Esperanza, Colmado Lydia and the Green Store are a short walk. Family Market in Isabel Segundo is the largest grocery on Vieques.

Christiansted and Frederiksted each have multiple walkable options. The bigger stores require a taxi or car.

For Coral Bay St. John, check out the Coral Bay Cruising Guide - https://www.cbycstj.org/coral-bay-cruising-guide
Cruz Bay St. John has the Dolphin Market walkable and Starfish Market that is better for a taxi.

Cheers, RickG