Besides the general safety advice offered, women traveling alone in South America should have few problems. Yes, in many cultures here, men have a very macho attitude, and women traveling alone can expect to get intense stares, catcalls, or even be followed for a few blocks by men asking for a date. But for the most part, these men are harmless. A simple "Déjame en paz" ("Leave me alone") will send the message that you're not interested.
There have been sporadic, unconfirmed reports of tour guides attacking single women travelers. It's always worth it to pay a few extra dollars to arrange a tour with a reputable travel agency. Talk to your fellow travelers and find out if they have had any problems. If you are attacked, contact the police immediately and notify your embassy. Safety specialists at your embassy will be able to assist you and hopefully work with the police to track down the assailant.
Note: This information was accurate when it was published, but can change without notice. Please be sure to confirm all rates and details directly with the companies in question before planning your trip.