I've caved and have commissioned someone to farm a set amount of boxes for me, because I don't think I'll have the time at this rate, with 37 librams to go still. But, when I farm skin of shadow I take the exrta time to pocket-pick the humanoids and guards in there, and the heavy junk box drop rate is pretty decent. I was getting about 5-10 boxes per run, which helps, and also slows you down enough to not get the annoying "you've entered too many instances lately" notice.
LBRS is definately the best place to farm boxes, and you can find many guides to doing so on the internet, so I won't add to that list here.
So, we have a little more than a month until Cataclysm, but wait, what about 4.0.3? Does this patch bring the actual Cataclysm and the world is changed forever, or is it just more content and events to be unlocked along the way and on Cataclysm launch day? If it's the former, that means I have much less time than I thought and I better hop to it. Hopefully Darkmoon Faire rep will still be attainable (should be considering the cards in Cataclysm).