I'm checking if this bus still exists on another forum. When I hear back I'll let you know.
On the other note. Ive paid for taxis from the airport to Marriott downtown 35pln (about $10), and from hotel to the airport also $10 not including tip (both times I gave the driver 50pln). But before you get to the taxi ask the driver how much it will cost to take you to your hotel.