I was talking to an American friend of mine about this because the issue was raised on PF that it is cheaper to eat out than at home in the States.
According to my friend's account, you can usually only buy huge packets of food in a supermarket and it is not cheap, whereas you can buy a ready cooked meal for one for very little.
I know one particular American who only eats take aways, can barely make it out of her flat she is that big and even eats off disposable plates to save on washing, I am not saying it's the norm but it is unthinkable here.
This is in complete contrast to what it is like here, the food in restaurants is more expensive and I would say of average quality (depending).
And despite the absolute horseshit you hear from some people on these forums, McDonalds is considered cheap, poor quality and just fast food (i.e. nothing special).
I generally do two shoppings for food here, one from super markets: Carrefour (I'd say average priced) biedronka (cheap as chips) and from a green grocers or farmer's market (very fresh, usually local, only in season, fruits and veg).
(like Gorący Kubek, powder soups, heat & eat things, deli items, microwavable dinners, etc.)?
None of the above, I can't remember even seeing a microwave dinner but they are probably there if I looked.
What percentage of the time (roughly) do you prepare food at home as opposed to eating out or getting take-aways?
I cook about 90% of my meals at home, the 10% is only if I work over time or when friends/family are over.
What is the rough proportion of the Polish to non-Polish food you eat regardless of the above sources?
I am not sure if you mean traditional Polish meals verses Thai or something or the actual ingredients.
I would not consider porridge a traditional Polish breakfast but the stuff I eat for breakfast most days, comes from Poland, if you know what I mean.
So most of the food I eat is Polish but not all of it would be considered traditional.
Best food in Poland is cooked by babcias, that's why milk bars (Bar Mleczny) sometimes have the best food for eating out and really are cheap.