I will be around Argentina, Uruguay and Brazil and was wondering what the quality of surf will be in the months Dec-Jan (southern hemisphere summer). The way it is shaped seems like it will miss out on any northern swell action, and that southern swells must be weak that time of year.... but then again, I've only been a west coast surfer, and therefore do not know much about the atlantic.

l am from Uruguay, l do not surf, but. l have friends that do surf and here in Uruguay you can go to Santa Teresa, in Rocha, to the beach called ''La Moza'' a lot of surfers go over there in summer to surf. And it is a very beautiful place, one of the best i've ever been. And if you want to visit some places in Montevideo (Uruguay is capital city) you can try http://hotels-montevideo.com they have very cheap apartments over there.
Hope this is useful to you. have fun.