Luckily for English speakers, this is the most common language to be spoken in lots of countries. This means that it can be very easy to get away with not learning any other language before you travel. However, there are also many benefits to learning even just a few simple phrases.
People may not speak a good enough level of English to answer your more complex questions. It’s important to remember that many countries educate children in English, but it is not their first language. This means that you may well experience language barriers when trying to communicate.
People may actually be more willing to help you if you know a few words of their language. The fact that you have learnt some of the languages will often be really appreciated and locals will be much more friendly towards you. It may also be very helpful when asking simple questions, like the location of a museum or a landmark.