Hi Aurelie,
I think there are a few French people in Kosice, we have a Cafe de Paris (makes and sells macarons) and French is taught as a second language from high school. One schools offers it as a speciality. There's an Allinace Francaise so you're sur to find activities there. I also speak French fluently (if a bit rusty) as we lived near Poitiers for 24 years.
You could try contacting Myriam Leclerc on Facebook. She was here for 2 years with her husband.
Good luck in your decision making,
Denise Sutcliffe