Template/Assets/Language.xml

<gs:GlobalizationServices xmlns:gs="urn:longhornGlobalizationUnattend">
    <!--User List-->
    <gs:UserList>
        <gs:User UserID="Current" CopySettingsToSystemAcct="true" CopySettingsToDefaultUserAcct="true" />
    </gs:UserList>
 
    <!--Display Language-->
    <gs:MUILanguagePreferences>
        <gs:MUILanguage Value="es-ES" />
        <gs:MUIFallback Value="en-US" />
    </gs:MUILanguagePreferences>
 
    <!--User Locale-->
    <gs:UserLocale>
        <gs:Locale Name="es-ES" SetAsCurrent="true" ResetAllSettings="false"/>
    </gs:UserLocale>
 
</gs:GlobalizationServices>