The best time to visit Martha's Vineyard is in the off season. I am not one for crowds or heat. While it is true that not everything is open, you could time it right before the season begins, or after it ends. Not only are there less crowds and but better parking too! On our first trip to the Vineyard we saw all the usual sights, Aquinnah, Menemsha, and Edgartown with the help of a great friend- thanks Grace! On our second trip we revisited those sights, added some new ones (Back Door Donuts, Alpaca Island, and the Chappy Ferry were some of our favorites), and enjoyed the drive around the island.
Somewhere around Edgartown