So if I am correct you mean 1500 is fairly enough for monthly food cost.
It gets cheaper as you eat home cooked meals made from available local ingredients in season exclusively at home, and gets more expensive the more you eat out in restaurants and cafes, the more prepared foods you eat, or the more meals you prepare with ingredients that are expensive in Poland, such as beef, lamb, seafood, or fruits and vegetables that are not in season, like tomatoes and peppers and just about any fruit except for apples.
Snacks and beverages away from home can add a lot to your costs. If you're very frugal and careful, a family of three can make it on 1000 PLN a month. If you're not careful, then 3000 PLN is entirely possible.
The biggest blow for you will be fresh vegetables and fruits, as well as beef and lamb. Poles eat very little beef and lamb, practically no seafood except for herring and a few very bland fish like pollock or Vietnamese catfish, and base their diet on pork and chicken, with cabbage, potatoes, onions and carrots being the primary, and often the just about the only, vegetables.
Oh, and by "food costs" I include household supplies like soap and clothes washing detergent, as well as personal hygiene products like toothpaste and toilet paper.