First, a little bit of geography. Chile, Peru, Ecuador and Colombia are on the west coast of South America. The East Coast is argentina and Brazil with just a teenie weenie bit of Uruguay.
Chile should be no problem. Peru will depend on the time of your arrival. It is not that dangerous, but the main highway is the Pan-American Highway, so if anybody wants to protest against the government, they tend to block the highway. It might slow down your progress, but nothing more than that. Ecuador get more complicated due to unrest, although it is still doable. Colombia... well, don't think about it. Chances are you'll end up in a FARC controlled area and as a hostage.
