I would strongly suggest steering away from department store bikes, not that there's necessarily anything wrong with the bike (considering the level of components, etc.), but simply for the fact that there will not be knowledgeable salespeople there to help with things such as sizing issues, nor will the bike likely be assembled and adjusted properly.
Of course, if you are knowledgeable and experienced enough to go it on your own on these issues, then go for it. But if you are that knowledgeable and experienced, it's not likely that you will consider a department store bike in the first place.
Be that as it may, if you want to go cheap, I think you'd be better off looking at Bikes Direct. Presuming that you can handle routine adjustments of brakes, derailleurs, and those necessary for fitting.