All you need to do is to add, for example, &uselang=eo to the URL of a LiveJournal page you're viewing, to read it in Esperanto. (Where "eo" is the language code for Esperanto.) If you go to another LiveJournal page, it will be shown with your normal language settings unless you add &uselang=eo to the URL again.
The codes for different languages can be found here: http://www.livejournal.com/translate/
