Ok, I created another sample that use 4 dropdowns (Country, Region, City, Suburb).  (Added it to the sample you can download here)

The last 3 are hidden on load.  One change, and the next one are loaded with data and shown.

If one in the chain are changed, those that are not required at the moment are cleared and hidden.

I can't put aside more time for this and hope you will investigate it further, but will update the sample in the future to come up with a re-usable bit of code.

I'm not too happy about the long script I got there, and asked for some expert advice in re-factoring where I know some real jQuery experts, eager to help are hanging around.

As for the other suggestion you were asking about, have a look how your original question changed.  Try stick to one thread = one question.