I heard that flying within South America is really cheap, but when I'm looking up the budget airlines (Gol, Oceanair, etc), a one way ticket from Santa Cruz, Bolivia to Buenos Aires, Argentina is 300 dollars or more! Would it be cheaper to book online in the United States or wait until I'm in South America? I'm afraid it would be too late once I get to S. America to book a ticket. I don't know where to go and what airlines are dependable. I'm traveling for 5 weeks from mid-July to mid-August. Any advice?