When to not use the articles?
In the second lesson, I've noticed these phrases:
"Adieu, les garcons!" and, "Bonjour, les filles!"
I guess I've never seen these uses before and it comes off awkward to me. Is there a specific explanation for this basic concept? More examples like these?
We tend to drop the definite article in English. It may sound awkward in this particular context, but what about: "Say goodbye to the girls, before you leave." "Goodbye [the] girls".
Individual addresses containing the article sound similarly alien to me, but are also correct: "monsieur le professeur", "madame le docteur".
This is a bit complicated. Try the french.about.com article --> http://french.about.com/library/weekly/aa082401.htm
It may not sound very correct when directly translated in to English, but it's definitely right in French.