When the family was young we used to take day trips often. We'd pile the kids in the car with a box of toys that only came out for car trips, a pillow and blanket for each, a bag with a change of clothes for everyone and...a cooler packed with food and drinks from home. Yes, part of the fun of travel is getting something to eat that you don't have at home, but doesn't eating travel food get old AND expensive fairly quickly? I think so.
As the kids grew we would travel more by air than car, making the cooler approach impractical. For short trips we'd pack some shelf stable supplies from home - most often meal bars and dried fruit which provided snacks and breakfast, reducing the need to eat out as much. For longer trips we'd plan in at least one visit to a local grocery store and always try to get lodgings with at least a mini fridge, if not an entire kitchen.
I feel the grocery store approach really cuts down on the expense of eating away from home. On a recent trip to Europe my spouse and I even managed to keep at this. I brought an insulated bag and we filled it at the grocers. Breakfast was included with all our lodgings but other than that we ate only two full meals out in five days, grabbing coffee or a snack here or there, but for the most part eating frugally from the groceries.
Whether you're on a day long car trip or a week long overseas getaway I encourage you to give it a try.