i always bring i food to movies, burritos work great bc they aren't very messy and easy to transport (i also drink beer in the movies, its too boring w/o it!).
food courts are for sure fair game for bringing food.
some restaurants don't care, especially deli style ones, or ones w/ outdoor seating. its safe to call and ask ahead of time or ask before bringing in the food. i bring food into restaurants pretty often, but it is technically not a "meal" just a few things i carry with me to help make boring veg food better: salad dressing packets (drew's has some vegan dressings and also can be found in to go packs), nuts or seeds, dried fruit/veg, and some crackers....anytime im stuck with a lame side salad or worse yet forced to order a fast food salad these ingredients help a lot to make food better. ive yet to be at a restaurant and be told not to use my own dressing or seeds, also these additions can be done discreetly if the situation calls for it.