Do you guys speak a mix of your languages?

Speak, rarely, but when thinking, yeah, exactly what you describe. Also, sometimes there's a concept that's just described better in one specific language.

For speaking I have more of a “switch” going on. Besides, I'm always mindful of people around me not speaking my other languages. On the other hand… when talking to someone who shares more languages, I feel we can achieve some nice compression by mixing and matching.