Nationals from the Gulf countries, including the United Arab Emirates, use a colloquial spoken language, known as Gulf (Khaleej) Arabic.
It sounds different than the Arabic spoken in other regions of the Middle East. The press, TV and radio and in government proceedings, use Literary Arabic, also called Modern Standard Arabic (MSA), which is not the same as colloquial Arabic.
Because of the large expatriate population, many of those in the service industry do not speak much Arabic, but instead the language of their native countries, often Urdu, Hindi, or Tagalog as well as English.
You will be able to get by fairly well speaking only English, as most people speak it to varying degrees, but knowing a few key phrases in Arabic makes life a lot easier.