There is no easy answer to this question – it all depends on the type of travel and work experience you are looking for. If you want to travel extensively and work only for a limited time, then depending on the type of job you get, you may not need to be able to speak German. Sometimes, in certain job sectors (such as IT and R&D) the working language may even be English.
Usually, though, you will need to have basic German, and a higher standard will be required for jobs requiring a lot of contacts with customers. But remember, learning some German is an effort well worth making! You'll be able to enjoy your stay in Germany that much more, and an investment in learning the language will be an investment in your future and your academic career.