On the railway from Perugia to Terni. (see below) Occasional buses from Spoleto
Don't expect buses from the village to meet trains unless this is confirmed by timetable. Not all trains are met and it's a huge uphill from the station to the town. Taxis come from Foligno so a taxi from Trevi to its station is very expensive.
The cathedral is difficult to photograph except from a distance but its a great place for walking around and enjoying the squares and the narrow streets.
Go into San Francesco church to admire (and if you can to hear) the wall pump organ that claims to be the world's oldest. It has been thoroughly restored.
- Ristorante Maggiolini in Via San Francesco 20.
http://www.ristorantemaggiolini.it/ [dead link]
It would seem strange to leave Trevi without having seen Spoleto.