<font face="Verdana, Arial, Helvetica, sans-serif" size="2">What I want to do is start buying HK - USA coach tickets on CO and use my HP miles to upgrade. But if CO won't let me exchange the miles, can I do that? </font>
Apparently, not. I just looked at the America West redemption charts on their web site, and apparently the only upgrades on CO that are available are those involving the 48 US states, Alaska, Canada, and Mexico. You could apparently get award travel (in coach or BusinessFirst) between HKG and the US using your HP miles, but then you'd not be earning miles for those flights.