Anything fresh from a market stall is likely to be wonderful. For a restaurant meal, try Sansavino in Place des Docteurs - they use fresh produce from the market and, although there is limited choice on the menu, what they do is done well. If you're a truffle-lover, try the penne pasta with truffles and mushrooms, it is unquestionably my favourite.
Stop by the antiques market (right & below) for a huge selection of vintage wares ranging from furniture to clothing to trinkets and everything in between. If you're not interested in buying, it's still a beautiful walk under the dappled shade of the trees, and there is a bar at the end if you're in need of a pick-me-up.
The markets continue into town, where you'll find fresh food. You can take food from the market into the cafes, as long as you buy a drink there to go with it.
Walk along the riverbank to see the bridges, which are really lovely in the summer light.