There can be only one default language for the entire Filr site.
When you create Filr users, you can select a locale for each user, which determines the language of each personal profile. However, when users who speak various languages work together on a Filr site, they can often see interface text that is not in their preferred language. For example:
Standardized group names, such as All Users
Login page
You cannot change standardized group names, such as All Users. Although the Filr login page can be displayed in only one language, you can change the page’s default language. You must be logged in as the Filr administrator.