Thanks for our advice! I already booked in Morro de Sao Paulo and looks as it's something! I'm not going much aroud because this are my "resting holidays". In Mendoza you should go to Puente del Inca. It's a beautiful place with only a Pousada were alpinists go before climbing ther Aconcagua. Do some research about it it's a magical place, quite lonely though. Other thing you might try is "Parapente" when I was there I wrongly asked for the shorter one (fearing that I could get dizzy) BIG mistake.
I live in Buenos Aires, so it's difficult for me to tell you were to go (nobody is a profet in it's own land). Buildings in downtown are vey beautiful, you can go to the outskirts of the city like "Tigre" were ther is a market and b taking a boat can have a barbacue facing the river. There are also lots of "country days" were you may go to a "estacia" and spend a "folclore" day. Barbacue, Pato games, horse riding... I don't find that very amusing, but it's OK.