Of course, the process is going to be different depending on where you are in Greece, but for the most part the rules are the same. You will need an unexpired drivers license to rent an ATV. Some websites will say that you need an international drivers license, but I've never been asked for one. If you want to rent a motorcycle, you will need a motorcycle license. You might be able to get by if you let the people know that your experience, but I highly recommend that you bring yours. It's as simple as that!