That's probably a question best asked at the store. To the best of my knowledge, all devices sold at the stores are locked to the carrier. This includes devices sold under and without a contract (full price). The last full price product I bought, was a nokia 6 yrs ago, and it was locked. But that was 6yrs ago with Cingular. I got the unlock code free from the internet.
Now, you're best off getting the phone at the carriers shop rather than say WalMart or Best Buy. I would explain to them, that you travel abroad quite frequently, and that you need an unlocked device so you can use a local Sim when abroad. If they're understanding, they will unlock the device free of charge. They don't Have to though, and could just simply tell you it's against company policy. But you'll have better luck if you buy a full price device I would suspect.
If you're not successful at the shop, then go on the net, and find a site which will send you the unlock code. Usually for about $10.
Keep in mind, some features will not work when you operate on a different carriers network. Like 4g for example. And you may not get OTA updates pushed to you.