Most likely you will have English as the default language.
If homework problems or other resources are available in your preferred language they will be displayed to you in that language. Otherwise they will remain in the language they were coded in. Course Coordinators can enforce a particular language to be used in their course. This will override the preferred language settings of all course members for that particular course.
Within LON-CAPA the default language of the user interface is English. User interfaces for other languages might not be translated completely, in which case untranslated words will appear in English. If you would like help with a language that is not completely available or not available at all from the language list, please submit a help ticket through Bugzilla.