Last year, I took a dream vacation to a place I had heard about my whole life, but never thought I would have the chance to visit: the Galápagos Islands. I swam with sea turtles and sharks, hung out with sea lions, and walked with the legendary giant tortoises. I traveled solo, skipped the touristy cruises, flew coach, and negotiated for some great deals, but my trip was nearly overshadowed by one major mistake: I didn't bring nearly enough cold, hard cash in the form of US dollars.