Mixing different languages (not programming languages :-) into one blog looks a little bit chaotic. Like reading English blogs on LiveJournal.com with a German browser. (They translate everything surrounding the English entries. Looks really funny.)
To be able to say some really important things (hehe) in my mother tongue, I've started a new blog called Dem Steff soi Blog.
There I'll mix two languages: German and a local German dialect. :-)