What a great question; and perfect timing! I am going to Ethiopia after the new year. I will be there for at least six months (I lived there for four years before). Packing space is at premium and I'm already weighing what knitting project(s) to take with me. Advice?
Seems like cotton would be the answer. I am not very good at knitting cotton but I have worked with Brown Sheep's Cotton Fleece and it was a lovely yarn. 80% cotton 20% fleece with lots of color choices.
Is there a knitting tradition in Ethiopia? What an opportunity to learn something new if there is - and what an opportunity to teach others if there is not.
if space is at a premium, I'd suggest lace or fingering weight yarns. Wool & wool-silk blends would be the lightest or you could throw in a cone or two of cotton fine. Another option would be to bring a whole lot of roving and a drop spindle and spin your own yarn once you get there! Have a great trip