Google Now and languages

I'm thinking about buying a Nexus 7, and I have a quick question about Google Now, which now supposedly works fully in more languages than English. I'm German and would like to select German as the default language setting in both Google Now as well as throughout the OS. How quickly can I change the Google Now settings from German to English (for voice commands) and back, and can I change the language in Google Now without changing the overall language settings?