Generally speaking, there are two basic forms of Arabic: standard and colloquial. The former is used by the media and in universities, literature and formal writing. If you take Arabic lessons from a Western school, this is probably the form you'll get. But, this isn't the way Arabic speakers use the language in their day-to-day lives! If you know that you'll be using Arabic mainly in one particular location (e.g. Egypt vs. Persian Gulf nations vs. Lebanon), it might be worth looking for an Arabic course that at least introduces the dialect of that area. On the other hand, of all of the Arabic dialects, Egyptian is the most widely-understood by all speakers (largely due to the nation's popular music, film and TV industry), so learning the Egyptian dialect is a safe bet too.