Returns the preferred locale of the given user or the site primary locale if the user doesn't have a preference set.
userlocale( user )
user: (Text) The user (or the username of the user) for whom the locale should be returned.
Text
The locale is returned as a string, such as "es_MX".
You can copy and paste these examples into the Expression Rule Designer to see how this works.
userlocale("john.doe")
returns en_US