Marhaaba! Salut! Hello!
These three words, all meaning "hello" should be understood by most people in Lebanon - and in terms of English, especially the youth and urban dwellers.
The official language in Lebanon is Lebanese Arabic, though many speak French as primary or secondary language (vestiges of their colonial past), and the use of English is growing.
Lebanese Arabic is one of the Levantine Arabic languages and is spoken nearly only in Lebanon. (Just as there are many separate languages descended from Latin - French, Spanish, Italian - there are many different families of Arabic languages, and variants and dialects of those).
What I find particularly interesting is that written Arabic differs from spoken Arabic - in fact, Lebanese Arabic is almost never found in written form except in novels when dialect is used. Formal publications like newspapers, as well as formal speeches, use Modern Standard Arabic, a standardized writing that's recognized throughout the Arab world. Modern Standard Arabic is nearly never heard of in conversation except for use in the news and again in formal speeches.
Then there's Classical Arabic, the language used in the Quran - many muslims study Classical Arabic with the aim to read the Quran in it's original language.
Lebanese Arabic is a rather guttural language, with a few sounds that are unfamiliar to us. I can write a transliteration of a word in our alphabet, but it won't give you a sense of it - you need to hear it to learn it. With that in mind, here are two videos from Free Language Videos that can help you learn a few words, like greetings and numbers:
Do you find pronunciation difficult?