You technically don't have to speak any other language to travel, English truly is the world's language. Learning some of the local language just enhances the experience, shows some respect to the local culture, etc.
Learning some of the language at home is good, but honestly you'll learn exponentially faster once you are submerged and see the language daily. You can even learn just by paying attention to the signs.
Expect to find at least a little English in nearly every place that caters to tourists. The more remote/rural you go the less English, however, you can still survive with gestures and smiles.
The famous Point It book can also help when you're really stuck! http://www.amazon.com/gp/product/3980880273/ref=as_li_ss_tl?ie=UTF8&tag=startbackpack-20&linkCode=as2&camp=217145&creative=399369&creativeASIN=3980880273
The language barrier is a pain in China sometimes, but then again, that makes up for half the "fun."