Thanks NormC - I wasn't trying to offend anyone by calling it 'ding Dong' just a bit of a joke. I lived in Vietnam for about a year and heard quiet a few Vietnamese refer to it as ding Dong - where's you sense of humour people!!
By the way, the maximum amount you can withdraw from a Viet ATM using an Aussie ATM card is about AUD$175 (or VND$2,000,000).

#10 said "where's you sense of humour people!!"
The word "ding" in Vietnamese has no meaning at all, that is why we did not put "ding" before "Dong" like the native speakers have joked. But we did call US$100 note in some funny ways.

Too many "ding dongs" don't sound funny anymore. It's more like confusion to me. However, I didn't feel it was an insult neither.

Thank you for great advice!
I think I'll just take some AUD to exchange in Vietnam, and also just use the ATMs over there. I'll also put a bit of cash on my Visa debit card. My credit union only charges the 1.3% conversion fee, so it's pretty economical.
Thanks again!

Unless your bank makes you pay a large fee for each time you use the ATM, there really is no point in bringing AUD with you: just use ATMs and your credit card. I find the exchange rates the bank charges when you use ATMs are usually really good too.
Now THAT was quite a song: Ding-a-Dong by Teach-In :-).