I think you will be happy with a small. I am 5'11" 185# and I wear a medium.
I can never pass up the sales at Patagonia. I've already spent way too much on their site this year. Tons of great deals at this year's Winterfest.
Picked up some microburst pants, an ascensionist jacket, some cap 1's, R1's, a few belts, and some things for my girlfriend.