ASA vs. US Sailing
I completed the ASA Coastal Navigation and Basic Keelboat Classes 2 years ago. I enjoyed them both and think everyone should take a Navigation Class. Reading a book on sailing and going out a couple of times with someone knowledgable might get you as much as the basic sailing class, BUT I still recommend the class.
If you log some of your actual sailing time it might mean more to a charter company than what class you took (as long as you took one). I have never chartered, so that is just a guess.