How much money should I allow for spending per day for a 10-14 day trip.
I bring not with me zl at all.
(Maybe 200zl for transport to nearest city.)
Take some cash in dollar, euro or what's best for you.
Then visit 5 - 10 exchange offices and ask what they can give for the amount you have.
You can withdraw zl in all minibanks all over Poland if you have Visa, MasterCard or other international cash- or creditcards.
The amount mentioned (500zl a day) is VERY much, in my opinion ... Unless you going there just to use a lot of money.