Im a big couchsurfer actually, drove across US by myself and couch surfed the whole way. If you have the right mindset its Amazing. Problem is now with its popularity there are a lot of people using it for the wrong reasons. Just make sure you check referances etc..
Anyway I was a single female from Australia taking on America and I never once had a bad experiance. I stayed with guys, girls, anything inbetween. Haven't surfed in South America yet but im heading there after Coachella.
http://www.couchsurfing.org/people/spero2/ If you have a look at all my referances you can see how fantastic my time was with everyone. Honestly I find it hard to travel any other way.