Yarnlove

I bought the lovely Rusted Root pattern a while ago, and am very much looking forward to wear it when springtime comes (even though it's been springtime since September) . The pattern suggests a 80% cotton/20% merino blend, which seems like an excellent option for a short-sleeved top. Cool like cotton, bouncy and elastic like wool. The best of two worlds. But what if you live in a country that doesn't provide you with these exquisite blends? Yes, I could order it from somewhere, but maybe I don't want to. Maybe I want to squeeze the yarn before I buy it, and make sure the colour is just right for me.

Dear blogreaders, what yarn should I go for? Suggested gauge is 20. Will pure wool be too hot? Will cotton drive me crazy? Am I too great a knitter to cave in for those tempting but common cotton/acrylic summer yarns? Please advise.