Is this the island tour by bus? I've been on it, and it isn't bad. We got to see a good amount of the Vineyard, and there were a couple of stops that allowed us to take in the area by foot. There was still plenty of time left after the tour to explore the area around Oak Bluffs, where the tender dock is located.
But if you'd like to go off on your own, doing so is very easy using the local (VTA) bus service. You can buy a day pass for $6 per person. To plan your day, the following sites may be helpful:
Vineyard bus map
Vineyard visitor guide - also contains information on each of the towns that comprise the Vineyard
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