English is widely spoken in Amsterdam, as well as other cities in the Netherlands, and you will have no problem navigating the city. Personally, I only know a few words of Dutch and I never had a problem in the city.
You may want to bring a phrase book to help you with greetings and simple phrases. Dutch people, like any other cultures, appreciate when you are making an effort.
The phrase book may also help you with pronunciation.
Wikitravel has a phrasebook that you may want to consult.