You can fly to Florence, Pisa or Rome with cheap flights of Ryanair or Easyjet.
By train: if you don't want to rent a car, it's easy to arrive here also by train. Sinalunga has a well connected railway station with Rome, Siena, Arezzo, Florence.
By car: exit off the Autostrada del Sole A1 at Valdichiana. Turn right for the signs Sinalunga-Siena and take SS26 Siena-Bettolle. After 5km exit at Sinalunga. Drive through the modern part of Sinalunga town following the sign for "centro".