Renting a car in Greece is easy and inexpensive. You can pay anywhere from $150-$200 per week for an "economy" car that would allow you the freedom to travel anywhere you want. "Mini" cars can be rented for as little as $100-$150 per week. Make sure that the price you are quoted includes all taxes, insurance, and fees (such as airport fee.) Use your international cell phone rental in Greece to rent a car easily.
The most popular way for visitors to get around is by moped. You can rent one in just about any small town in Greece, and at about €10 per day, they are a bargain. To rent a moped usually one has to exhibit a driver's license (a Greek or international licence is not required most of the time), pay the daily fee, and to leave a passport as guarantee that the moped will be returned.
While renting a moped is the most efficient way to get around the immediate area, they do become dangerous in the hands of an inexperienced driver. While most opt for the complete freedom of feeling the wind through the hair, wearing a helmet is strongly advised. The roads around Greece, and especially around the islands, are narrow, ill maintained, and car drivers drive like, well, Greek drivers. Mopeds are responsible for many tourist deaths every year, and for countless visits to the emergency room. Use your Greece cellular phone rental to rent a moped.
The intercity bus system in Greece is very efficient and if you do your homework you can travel anywhere in the Greek mainland with the "KTEL" (intercity) green colored busses. Every city has a KTEL bus station and the locals would be happy to direct you. The bus system was never created to accommodate tourists so you might run into the language problem. Best thing to do is to find one of the other Greek travelers who speaks English and ask for assistance. Most young people in Greece speak a little English and most would be more than happy to assist you.
Ferries and Boats
Getting to the islands would require either a short flight from Athens or Thesaloniki, or a boat ride of varying length.
For islands close to mainland hopping on a ferry is your best option. Keep in mind that most of the ferries may make several stops on different islands en route to their final destination. Many islands have airports and you can catch a short flight from Athens International Airport or Thessaloniki. Islands close to Piraeus are connected with "Flying Dolphins" that are very fast and efficient. They don't offer the charm of seafaring, but will take you to your island fast.
From the 16 international airports of Greece only Athens and Thessaloniki receive regular flights from abroad. All other airports in the islands and towns of the mainland are served by frequent connecting flights from the two large cities and during the summer they accommodated numerous charter flights. The distances within Greece are small, so the furthest destination would be about half hour flight from Athens. The Greek carrier Olympic Airways and its subsidiaries offer the majority of flights within Greece. Use your international cell phone rental to make ailine reservations.