Yes, ATMs are fairly common in main towns and resorts in Greece, although they may be hard to find in rural areas. They accept debit cards from most major credit card companies. Many machines have an English language option. In Samos they are at the airport and in Vathy, the main town,  and Pythagoreio, Karlovassi, Ireo and Marathokampos.  The addresses can be found on your credit card company's online ATM locator.  Sometimes the ATMs are in a room outside banks but ATM cards will open the locked door. Banks in Greece tend to be shut in the afternoons and at weekends. Travellers' cheques are no longer widely used. Some banks are now reluctant to accept them although currency exchange offices will take them if they are in euros.