It is true that it will be - in general - very tough to beat the US prices (sales + rebate offers, etc). However, if you intend to stay in PL for an extended period, it would be advantageous to have the warranty coverage there (most purchases in the US will not be accepted elsewhere, unless you pay for international coverage).
Unless you can speak Polish, a laptop purchased here won't be much use.
Not necessarily so. I managed a language switch in Windows (Vista?) several ago, so I know it can be done - and quite easily at that (took me <2hrs including google searching for instructions). In addition, most of the computer literate sales people speak some English and I bet if you were to use your personal charm and asked nicely, they could do it for you free of charge with the purchase of the new machine.