What should I do if I've enrolled in a badly organized course?
I have seen cases where the instructor is given a module just two weeks before it starts, has no time to prepare, and might not have the proper background to teach it. 

You might consider that the instructor is doing his/her best with what they have to work with. You might consider talking with the instructor to see what they believe you should be doing in order to succeed in the course. If they say "read the book" then you should read the book and study with little support. 

Not all instructor are good and some are good but in a bad situation (that is, a situation not of their own making but rather one forced upon them). Either way, talk with them and find out what you can do to succeed.