|Google Maps help: Directions language.|
|You can select the language in which the driving/walking directions will be given:
Directions in english.
Directions in dutch.
If you want to change the distance units (for example: km instead of miles) you must change the generated code.
opts.locale = "<languageCode>";
And add/change the country code:
opts.locale = "<languageCode>_<countryCode>";
opts.locale = "en_US";
More information about countries with their corresponding language codes.