What is the best way to get a user to view a site in another language?

I have a multisite install with BP. I was hoping to use the languages at sign up plugin, but found out that the plugin does not work with BP. Since that option is not available at sign up, does anyone have a suggestion on how I can have the user choose a different language for the front end without the admin interface? I know that there are a number of plugins avaiable, but I was hoping to not have to use a non-WPMU plugin. Thanks in advance.