Wanna see a city on a budget? Pack exercise clothes and a pair of good running shoes.

Your per-trip outlay will be nil and you'll still get to see what a city has (or doesn't have) to offer you.

The single biggest waste of money for pilots on the road, IMO, is alcohol. Having one beer once or twice a trip isn't going to bankrupt you, but those folks who sprint to the bar are ****ing away their per-diem.

As for food expenses...as others have said, pack a small cooler. I used to get 2 full days of food out of a small soft-sided cooler. That provides flexibility if you want to go out with the crew or have a specific meal somewhere, but allows you better control cash outlays as well as the quality of the food you consume.