How to have some sites in French, some sites in English, but keep the back end in English


I did a few searches and found some answers but not exactly what I needed. I have some sites in English and some that will be in French. I uploaded French language files but only the backend appears in French.

I need it the other way around – for the admin Dashboard to stay in English, but content and such (anything the viewer would see) to be in French.

The French sites do not share content with the English sites. Should I have 2 separate WP multisite installs? Or can I keep them all in one network, and use something like QTranslate? If so, is there away to enable French on designated sites and English on the others?

Thank you, Leah