Take a cab - About $70/80 per cab each way plus tip.
Never visited, never tasted any of their expressions.
Without a good tasting, no interest in a visit.
There should be reviews on TripAdvisor.
If considering a Distillery visit and wanting a scenic visit and a clean/sanitised tour, then Depaz or Clement on Martinique (both good Rhum).
But for a real experience with steam driven leviathans, with Rhum made and bottled by hand, then La Favourite is a must. Their Rhums are superb, especially La Filbuste.
La Favourite tastings are noted because all Rhum is there, with the shop prices equal to and sometimes lower than Duty Free at Port. Port Retailers are there to make a profit.