Yep, I would second what patrick92260 said. I did something closely to that last year, and got my iPhone off-contract on 2 days after the launch date.
What I did was I just walked into the store, grab the queue card, not really mention about off-contract or anything until the phone was out from the back door and he started to scanning my phone. Then I said
I'd like to buy this phone off contract, is that possible? He said yes, then he was amazed by the full price (it was over $1,000 w/ Apple Care+) Then I gave him the CC, and done. It's that simple.
I'm planning to do this again this year as well I don't really want to be in the contract (with the potential that I could bring this phone w/ me when I'm aboard)
Remember, don't ask about the unlock just don't. State that you want to buy it off-contract, then they'll sell you. If you said you want an unlocked one, they will not sell you one.
(BTW, kudos to MacRumors news that said people got the unlocked iPhone from off-contract phone last year though. That gave me a courage to go and stand in line for the phone.

)