Which dialect to learn?
Egyptian, no question about it! Part of the reason is that I am Egyptian,
that should be reason enough! No it isn't? How dare you!! Okay, how about
the fact that it is universally understood allover the Arab world, that
it is easy, that there is a lot of material and people abroad with which
and whom you can practice Egyptian Arabic. If not Egyptian the second choice
is Levantine, if not then don't bother, other dialects are too local to
be worth the effort.
Can I learn MSA/classical
only?
Of course. Every literate person and most illiterate people will probably
understand you perfectly if you speak classical Arabic. However, you would
probably have some problems understanding what they are saying, you will
be cutoff from TV, from normal conversations and from the souls and minds
of people. Plus everyone will probably laugh when they hear you speak classical.
Can I learn colloquial only?
Yes, many people do that. This will, however, cut you off from all
written material, most arts, and from news. To watch al-Jazeerah you would
probably have to learn classical/MSA.
How can words be uniquely
understood if they are written without vowels?
Remember that Arabic doesn't write only short
vowels, long vowels are always written and remove a lot of ambiguity. Moreover
the structure of Arabic is so that very few words derived from the same
root will have the same consonants. So in the end the ambiguities are not
more annoying than the word read in English and even easier to discern
from context.