I hope that this article will help you during your stay in Poland!
In the past all foreign tourists were forced to exchange certain amount of money every time they were crossing the boarder according to the official (poor) course, not anymore! People from Western Europe and the USA were also forced to pay higher rates in the hotels than people from Eastern Europe - not anymore either. In spite of the fact that Polish "zloty" (Polish currency) is interchangeable into dollars (there is not anymore "official" and "inofficial" exchange course) Poland is still a relatively cheap country for the foreigner from the Western Europe and the USA.
There are some precautions that you need to take into account before your travel to Poland:
Better use public transportation than rent the car. Car insurance is very expensive, one of the reason, many cars, especially the expensive western brands are stolen by car Mafia's. Besides, the road system is poor, there is not enough highways and freeways in the country. Traffic on the streets of many towns is also high (lack of beltways) and it makes driving inconvenient and expensive (gas price is high compared to the USA). Polish police also can take advantage of naive and rich foreign tourists and they are first to get tickets. Public transportation system is cheap and comfortable. It includes trains, buses, airplanes (between some cities) and city transportation system like trams, buses, metro (Warsaw) and of course taxis. Be careful with the taxi. Some taxi drivers may charge you higher rate especially if you are at the airport, Warsaw airport is the worst. I know that police tried to solve that problem but I am not sure whether they did. For instance the best way of transportation between Krakow and Warsaw is an express train, but the best transportation system between the Warsaw and Wroclaw (Breslau) is to take an airplane.
Do not do any money transactions on the streets. There are money exchange offices (kantors) almost everywhere and they do not charge a fee for a transaction and are safe to exchange the money. Some locals want to take an advantage of the foreigner. Do not try to look too much as a rich foreign tourist with expensive cameras hanging from your shoulder and do not speak too loud your language because you would be exposing either to a thief or people would continuously ask you for money or to do some questionable deals.
Credit cards are used rarely and only in big cities (expensive restaurants, hotels and some stores). Travelers' check are changeable into money but some fee applied.
I recommend Berlitz Polish Phrase Book
Eyewitness Travel Guide to Poland (Eyewitness Travel Guides)
by Teresa Czerniewics-Umer, Malgorzata Omilanowska, Jerzy S. Majewski, DK Travel Writers