Martha’s Vineyard is an island bigger than it looks. You definitely need transport to get from town to town.
Sometimes people visiting Martha’s Vineyard for the day make the mistake of taking a Steamship Authority ferry into one town (Oak Bluffs or Vineyard Haven) and out of the other town. You need to know that Oak Bluffs to Vineyard Haven is a substantial distance especially if you are walking in the summer heat.
Public Transport Options
The Martha’s Vineyard Regional Transit Authority runs buses all around the island.
Alternatively there are taxis that can take you around the island.
Uber hasn’t really come to the island. Friends who have tried to use it have had very little luck.
Rental options from motorised ( cars and jeeps) to manual (tandem bikes, electric bikes, regular bikes).
You can rent a car pretty easily from either the Martha’s Vineyard Airport, or the ports at Oak Bluffs or Vineyard Haven. It won’t be cheap though.
At the end of the summer, sometimes the car rental agencies will let you take a car off island (a car rented off island and then left with them when the renter took an alternative means off the island).
Driving on the island is actually pretty easy even if there are no traffic lights. A few years back, there was an uproar when the island put in a traffic circle (a round-about) in a particularly busy 4 way junction. Islanders do not like change.
You can also rent bikes from either Edgartown, Oak Bluffs and Vineyard Haven. There are lots of bike paths. Even if you are not on the bike path, cars are suprisingly courteous to bikers. Those crazy drivers from Boston and New York? They are surprisingly polite on the island.