Nearly all Dutch people speak good English, and if they hear you speak Dutch with a foreign accent, they will probably turn to English immediately! Nevertheless, learning some of the local language is highly recommended. It will help you to settle in, and the locals will appreciate that you have made the effort!
To get official recognition of your Dutch language skills (in order to work, for instance), you must follow a course that offers exams within the NT2 (Dutch as a Second Language) structure. This is administered by the Dutch Ministry of Education, Culture and Science.