I don't understand why, but for some reason, unless I pay 2000 dollars, it is impossible to fly to Lima, Peru on Star Alliance from SEA... although looking at the Star timetable, it is very doable with many different flight options.

Guess I will be stuck on LAN or Continental. (Any tips for staying *Alliance would be greatly appreciated if anybody has any)

Bolivia I did once on STAR through GRU, but that was a round about way to get there. I just happened to have the time. Very nice crews on the SA flights to GRU / EZE out of IAD though. Never had a bad experience yet.