I am wanting to set everything on Mt Gox up in my local currency (Aus) because from what I understand it saves me from various conversion charges.
But if I put up a sell price in Aus dollars, how will that work with buyers? Will it limit my potential to sell internationally? Or will Mt Gox system just automatically adjust it to the currency of the bidders?
Essentially, your sell order will only be taken by buyers paying with the AUD in their wallet. There is some chance that a bid on another market (e.g., BTC/USD) is so high that Mt. Gox will do the conversion and buy your BTC/AUD offer and they would pay in AUD even though the buyer had a different currency. Arbitrage is what keeps the various markets relatively equal in price. (after considering the AUD/USD.)