You are going to have a fantastic trip for sure. South America is my favourite continent to visit, I love it.
I have not been everywhere you are going but the highlights of places that I did go to:
Inca Trail/Machu Picchu/Cusco
3 or 4 day trip/Salar de Uyuni on from San Pedro de Atacama to Uyuni (or vice versa)
Iguassu (Argentinian side best to stay; Brazilian side best overall view, but not much else to do; town just inside Paraguay, Ciudad del Este is worth giving a miss though)
Colombia was my favourite country: people amazing and beautiful place (recommend Medellin - paragliding ace; Cartagena; Salento; a couple of football matches were easy enough to just turn up at - best atmosphere ever in teh away end with America de Cali fans; the women are amazing too; this is one country I am going back to)
Rio de Janeiro (hang-gliding cool there too; can get to a football match at Maracana easily enough, including transport; Marius restaurant on Leme is amazing)
Torres del Paine hiking, beautiful
Isla del Sol on Lake Titicaca
Battlefield tour(s) and walk around mountains outside Stanley in Falklands + Sea Lion Island - would like to have spent more time here (not Stanley though - other islands)
I noticed you missed out Venezuela, but you seem to go from the Amazon to Guyana - I haven't been there, but I would love to go to Canaima NP in Venezuela and it seems like you could do this, so I would look at it. Looks amazing, the "Lost World" scenery. I will go one day, high up on my 'list'.
You can get by with a Spanish phrasebook but will enjoy it more learning the lingo and using it - you will be fine on that count.
Marching Powder is a good read.