Acadia Nat. Park is a fairy tale place; absolutely gorgeous IMO. on the other hand, Bar Harbor is one big tee shirt shop for the tourists that don't like the outdoors.
June is probably the worst month for bugs. Earlier than that is usually too cold (although this has been a mild winter). I've been there in August and the bugs were gone by then.
I fly into Bangor and rent a car for the hour drive to B.H.
Ellsworth is only 20 minutes from B.H.
Try contacting the Chamber of Commerce there. Maybe they can give you up to date info on shuttles and the like. Also, contact the rangers in the Nat. Park.
"Life is a Project!"