Make sure they teach you HOW to teach not just WHAT to teach!!!!! I.e. Have a look or talk to them about how much they cover on PMI.
Have a look at the classroom equipment, do they have projectors? do they already have briefing material for you to present?
Finally, for anyone who is currently an instructor, what sort of time should a full time course (4-5 days per week) take from first starting to test day?
I would say a full time course should take at least 8 weeks. They will all tell you less but expect that much, possibly up to 12 weeks. Delays can come from getting a CASA FOI to test you, aircraft going U/S, bad WX especially in SE Qld over summer, however the usual cause of delay's is the flow on effect of instructor candidates taking an extra 10 mins here and 5 mins there to get ready especially by the end of the day when everyone is shagged leaving a little each day to be carried over to the next.
You could try asking the bigger schools like China Southern WA Flying College, Flight Training Adelade or Singapore Flying College about where they typically hire new instructors from and go learn there!
BTW: the US FAA Instructor's Handbook is gold if you can get your hands on it