Written (formal) arabic is a different story though, I think that's what's commonly taught for non arabic people
But even within these dialects, there are regional dialects that might be difficult to understand even for native speakers from that same country.
For example, Tunisian Arabic can (roughly) be divided into northern and southern dialects. I've met people in the north who think I'm from Libya because of some words that are shared with southern Tunisian Arabic. Tunisia is a relatively small country, so imagine the variation in dialects in Egypt!
If you're interested in learning Arabic, don't let this scare you! The "generic" Egyptian, Lebanese, and Syrian dialects will easily be understood by most Middle Easterners and a fair chunk of North Africans.
But note that Egyptian Arabic is very different from Lebanese and Syrian Arabic (which both are in the Levantine Arabic family).
Given that learning the language (in any form) is probably going to be a huge challenge the prospect of spending years studying the idiom only to end up in an arabophone country and not being able to fluently converse with anybody felt discouraging.
I eventually decided that I would focus on learning Russian instead, an other very difficult but obviously completely different languages (although it also features declensions and relatively simple conjugations minus the aspect thingy).
Do you think I was mistaken?