Buses for Hunyuan leave from the main bus station in Datong on Weidu street (see attached maps) and cost 25 CNY. In Hunyuan, the bus will make several stops. The stop for the monastery is next to a gas station. Show the driver a picture of the monastery if it is not clear which stop to use. At the gas station, there should be taxis waiting to take people the rest of the way. Price for the taxi should be about 20 CNY. Taxis may be shared with other people. If possible ask a local how much they are paying and pay the same amount.
To return to the Hunyuan Bus Station, tourists are at the mercy of the taxi drivers because there is no other way out. The price will be higher and it's best to find someone to share a taxi with. The price will start at about 50 CNY and it may be a little flexible. The taxi will go to the Hunyuan Bus Station which is only about 3-5 kms from the monastery. Buses to Datong leave frequently and cost 25 CNY. Buses will return the Datong Main Bus Station and stop on the big road outside the station.