Can one use AA mile to upgrade on a partner airline? Our agent is booking a multi-city Australia trip for us. We'll be going Premium Economy between LAX and Perth and would love that portion of the trip to be business class if possible. Do you think that's doable? I keep hearing different things?

no, just for award tickets.

per aa.com

Upgrade awards are only valid on individual published-fare tickets on flights marketed and operated by American Airlines and are subject to capacity controls. Co-Payment is non-refundable and inclusive of U.S. excise tax where applicable.

Even Hitler couldn't get an upgrade on Qantas: http://www.youtube.com/watch?v=eg5EEpXBBKQ

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Vic's travels: http://my.flightmemory.com/vogilvie

I think you need to check your airline itinerary - as the flights from LAX all go via either Sydney, Brisbane or Melbourne.
From these ports they seem to use a different aircraft and these don't seem to have a Premium economy section.

Poor 'Hitler' - we have had 100% success with Qantas upgrades the last three trips to Europe. We are Qantas frequent flyers - so I guess from what has been said it means the Oneworld and American Airlines relationship won't help you.

If they get the A380 back running that is apparently really good in premium.

Good luck!

Oops - just realised this is an old post and the OP has probably been and gone.