Dear Sue,
Best of luck on your trip. When you reach South America, get a bus south from Santiago to Tierra del Fuego (ferry from Puerto Montt). When in Peru miss out Lima at all costs (it's a horrible hole) but visit Cuzco and get the train to Macchu Picchu.
Quito, Ecuador, is the most unspoiled of the South American capitals. As you are not pushed for time, visit Guatemala and get a bus, not the plane, to the ruins of Tikal in the Peten jungle: unforgettable. The highlands around Chichicastenango worthwhile also. More detail if you want it and nearer that part of your odyssey.
Andrew Baynes (61)