Public buses have their base in capital Fira and run through a network of several destination in Santorini island: Fira, Pyrgos, Perissa, Kamari, Airport, Oia, Vlyhada, Faros, Akrotiri, Airport, port.
The public buses company webpage is http://www.ktel-santorini.gr where you can find the detailed timetable of buses (check the services section)
Pyrgos is serviced by a bus that runs along the Fira-Perissa route. Pyrgos stands in the middle of this route. The bus station is located in the Pyrgos central square, for both destinations (Fira, or Perissa).
It is very important to note that, every hour, only one bus of the Fira-Perissa route passes through Pyrgos. Other buses bypass Pyrgos, at 2km away.
A useful rule for estimating when to wait for the bus is this: