Are you non-reving or with positive space? I ask because the route you chose is good; returning from Buenos Aires should be less challenging than from SCL. Why? because cargo loads are usually heavier from Chile than from Argentina and some times the flights will leave with no non-rev passengers even with empty seats because of the cargo. This is worse during summer so if you go now it should not be a problem. It's winter now and Buenos Aires has it's first snow in about 90 years.
Try to learn at least a few phrases in Spanish; folks will appreciate it if you make an effort.