Samos is too big to manage easily without wheels. KTEL buses connect Vathy with Pythagoreio, Kokkari, Karlovasi, and the airport on roughly hourly schedules in summer; off-season service drops to a couple of buses a day.
A rental car opens up the inland villages and the western half of the island; expect to pay around €30–€50 a day in season, half that in spring or autumn. Scooters work well for the south and east coasts but the road over the Kerkis flank to Karlovasi and beyond is long and winding. Taxis are reasonable but few; book by phone rather than waiting at a rank.