English is not the most common language on the planet (
my updated method of generating gismu uses data from here http://en.wikipedia.org/wiki/List_of_languages_by_number_of_native_speakers) and English is No 2.
I guess you just don't see any method of overriding this but I hope I can fix that soon. LMW will be opened in the language of your browser (for those who are not logged in).
Making Lojban the default language in LMW indeed would force us to write articles in Lojban first and therefore increase our own lojbanic skills (this idea was mentioned in IRC by la tsani ku .io)