In Poland the official currency is zloty (PLN), often abbrieviated to zl. You can exchange all major currencies into zloty at many places in Poznan (banks, currency exchange office - kantor). The current exchange rate is app. 3.2 zl for 1 USD, 4.2 zl for 1 Euro and 5.00 zl for 1 Pound. The rate can vary from day to day. Also, it is now easy to get cash advance on major credit cards, at several ATM's and banks located downtown and near the faculty.
NOTICE: Usually using your credit/debit card at the cashpoint/ATM (Bankomat) will give you about 10% worse exchange ratio than kantor!