my recent research would suggest that cologne isn't a spectacularly good city to visit from a tourist point of view. dr kruger's sex shop was quite illuminating, but other than that it was cold, wet and rather dull...
koln even...
I've not been but heard good things about Gdansk, might be worth trying. Anyway wherever you choose it's pretty cheap and the Polish are a good crowd, friendly, open and good fun. Importantly the girls are attractive and some complain that polish men aren't - so that's good for the chances.