Where to eat? I admit I have eaten crêpes from the guichets standing on the sidewalks. But benches, oh the benches! They are in the the grand parks with magnificent statues, but also in church courtyards & along sidewalks, and near so many architectural wonders! (And probably other places I have yet to discover...) If it is raining? Portez toujours un parapluie!
Why not eat in restaurants while traveling? Obviously to save money, lots, (which you can then spend on books & scarves!) There's more: by eating outdoors you can spend more time enjoying the amazing buildings & action of Paris. Benches are my friends & support while sketching, & also my favorite form of restaurant.
I recently learned the expression, "se mettre dans la peau de quelqu'un.", to place yourself in another's skin, to see their point of view. I understand that restaurants are a big form of entertainment for many tourists, so I know my way is not for everyone.
N'importe où, bon appétit!