The guide / leader can almost always speak the local language / dialect at least at a minimal level. Similarly the local people can speak and understand Vietnamese.

See also other FAQs

How does tipping work in Vietnam? Do you tip in Vietnam?

What is an on-site tour guide, tour guide and tour escort / leader?

Are your tour guides / leaders licensed?

Do your local tour guides speak English well?

What languages can your tour guides speak?

Does the leader / guide hold any formal qualifications?

How long has the guide been doing similar tours?

Are any of the leaders guides first aid trained?

What training has the leader / guide received?

Guides can speak English to what level?

Sufficient number of trained and experienced staff?

How many guides & porters are employed for the expedition?