I read in the New York Times that the Obamas had been to La Fontaine de Mars for dinner while in Paris last week. I don't know the restaurant scene in Paris that well - -so I thought it was funny that this place IS one of my places that I always visit when I'm in Paris. It's a charming spot near the Eiffel Tower in the 7th. It has that classic bistro look and serves non-fussy food like freshly sliced country ham, escargots, steak frites, daurade... etc. etc. And they have a nice wine list with a wide selection of prices to suit everyone.
The location overlooks a charming fountain (thus the name) and there is outdoor seating in season.