You can use them, but I wouldn't recommend it. If someone steals the number, you're out hard cash until you get it fixed. Even with good anti-fraud procedures, you can still have problems with checks bouncing if it happens at a bad time. Since it's overseas, the dispute process might take longer as well. Since you'll be a tourist, you'll be a target, and since you'll be in tourist areas, you're a likely target.
You're much better off using a regular credit card or carrying traveler's checks (or using an ATM -- that would be my preference). From what I remember, the Cirrus network was much more widespread than Plus in France so check the back of your card to see which it has (pretty sure you have one or the other, not both).