What you mean by "the centre of Crete" where you are staying, which town it is? What do you plan to visit from there for sure?

Having lived on the island myself, I can only answer the practical aspect knowing all that. For the economical costs; if every other day without car you will rent a scooter it will be more expensive for sure. There are great weekly rates for car hire that equal a three day hire.

Do note that not every place along the coast is suitable to visit by scooter, so for the best advice really the town you are staying and plans where to go are a must know to help out better if a scooter can do the trick.