I spent 9 months backpacking from Guatemala to Buenos Aires. There are thousands of people who do this sort of thing every year, and you'll meet lots of expats. In fact, until you hit Colombia, you probably can get by without knowing much Spanish. Personally, I would just skip this article, buy the Lonely Planet and live a little. Some places that I'd recommend seeing:
http://wikitravel.org/en/Antigua_Guatemala
http://wikitravel.org/en/San_Juan_del_Sur
http://wikitravel.org/en/Tayrona_National_Park
http://wikitravel.org/en/Cusco -- You hang out here when going to Machu Picchu
If I were going today, I'd probably stop in Santiago a see what's going on with StartUp Chile: http://startupchile.org/