I would not truck a sleeping bag along for the whole trip just for a few nights on the Inca trail. Get a liner, and rent the bag from them. It can get COLD up there, and you do not want to show up with the wrong weight of sleeping bag. I do not know what company you are doing the hike with, but when we went, the sleeping bags were very clean, and only used 3-4 times before they were cycled to their guides/porters to use. You are trusting them to get you over the trail safely, feed you well, yet you are worried about their cleanliness standards? Granted it was over 10 years ago that I spent weeks backpacking there - but I can tell you that every place I stayed in Peru was cleaner than most of the US hotels we stayed in just recently. Ick.