Which city's residents would speak dzongkha?

Dzongkha is the national language of Bhutan, so any city in Bhutan would speak it, such as:

Thimphu
Damphu
Jakar
Mongar
Paro
Phuentsholing
Punakha
Samdrup Jongkhar
Trashigang
Trongsa
Dzongkha is the national language of Bhutan, so any city in Bhutan would speak it, such as:

Thimphu
Damphu
Jakar
Mongar
Paro
Phuentsholing
Punakha
Samdrup Jongkhar
Trashigang
Trongsa