I went to Martha’s Vineyard just before the 4th of July (stayed from June 29 to July 3). Obviously a peak tourist season. I also brought over my car by ferry. It is not as crowded as I thought. During the day all popular spots, especially in downtown areas, are crowded. So during these peak times, I went to other parts of the island and often found myself alone with a occasional people walking or biking past. Whenever I want to go to downtown, it might be a search for some parking. The further you go away from the center, the better parking is as long you don’t mind some extra walking. My only issue while geocaching is finding an access to trailhead or starting point to hike for some caches. Several location has private only signs. If I decided to come back, i would bring or rent a bike where I feel can receive better access by bike instead of driving around looking for vehicle access for some caches. Overall it is very doable to go, even during peak season, with a car and a bit of patience.