Lots of good riding in Portland and at Acadia. If not bringing your own bikes, check out CycleMania in Portland and Bar Harbor Bicycle in Bar Harbor for rentals. Carriage path loops are a must on acadia, and will take you almost everywhere you want to see. Lots of good riding around Portland, I usually end up recommending a loop through town, and then down to Portland Head Light, and to a beach if you're in to that. Eastern trail is great if you're looking for some riding on gravel, but if you're not looking to put up miles, there are better ways to see the area