The excellent Pilot map of Elbląg is available in most bookshops in Gdańsk, petrol stations en route and kiosks for about 9zł, and includes street plans of several towns in the area around and including Frombork, and also has an excellent map of the Polish coast from Gdańsk to the Kaliningrad border. There is just one ATM in town at ul. Mickiewicza 5 and many of the places in town (including Cathedral Hill) only accept cash. Make sure you take enough money with you to cover your expenses.