Transportation in Santorini is limited to buses and taxis. Buses run regularly between the major towns and attractions, but can be crowded during peak season. Taxis are readily available but can be expensive. It is recommended to rent a car or ATV for maximum flexibility, but be aware of the narrow and winding roads.
If you have more time, consider adding a visit to the village of Megalochori or a day trip to the neighboring island of Ios. If you have less time, consider skipping the hot springs or the sunset cruise.