Hey there,
I would say Japanese is best for the airlines - as they are one of the main players for tourism in Oz.
In terms of learning a language - I don't think a summer course will quite cut it for you. It will be great for giving you an introduction to the language but that's about it.
As someone who has lived in Japan and taught in Japan, I was there for 1.5 years, and am no where near fluent at all.
Fluency in Japanese comes at around the 3 year mark, and this is from even living in the country. Most of my firends who speak it fluently said it took them that long, and that was studying daily too.
Hope this has given you an insight.
Enjoy your weekend,
Raver
