Renting a car is a pretty good idea in Hobart, particularly if you want to see the greater area as public transport can be a bit infrequent. There are heaps of rental firms in Hobart, so you shouldn't have much trouble getting a decent deal. Tasmania is one of the few places in the world where hitching is a plausible option - if you want to hitch a lift out of Hobart, catch a bus north to Bridgewater or east to Sorell for starters.