Hmmn, I am in two minds about the pre-employment aviation courses.
I absolutely believe that the one day courses, or the ones held over a few weeks are most likely a waste of money.
However, I studied an International Tourism and Aviation deg at Uni with an International Flight Attendant elective and I found it extremely helpful. However, this was two years long and taught us everything from t he ins and outs of Visas, customs and immigration laws and even papers on contractual law and senior CC management. As well as things like the ins and outs of a variety of different aircraft etc. So it was very extensive and well worth the hefty student loan. It's also held me in good steed for the interviews I have had (and positions I've been offered in the biz). The interviewers have always asked questions about it and looked suitably impressed.
So, my point is, unless you are going to fully dedicate yourself to an actual Dip or Deg, I'd say don't worry about it. Other people that I work with that have down F/A short courses have said it's been a waste of time. Although one girl I worked with did the Air NZ pre-emp course, and ended up landing a job with one of their small subsidiaries. So maybe it works after all??