We also only bring US dollars. We charge whatever we can on our Capital One Venture Card, which gives us 2% cash back, and doesn't charge either a foreign transaction fee or a currency conversion fee. On the French side, we always ask that the charge be put through in Euros, so that we get the current conversion rate. Many establishments have their own conversion rate, which may be better or worse than the actual current rate. While we use the credit card whenever we can, we also make sure to have the amount of cash with us that we expect to spend that day, as you never know when the internet might be down and the credit card can't be run.