iOS 4: Stuck in DC and too timid to upgrade

Just my luck to be stuck in Washington DC when the new iOS4 is released. And, of course, I’d travelled with my iPad and left the MacBook Pro in London. So how to upgrade the OS without access to the home mothership? Not so easy it seems. I asked at three separate Apple Stores, including the new Georgetown branch, and got conflicting responses that didn’t fill me with confidence. You see, I don’t want to risk losing my data. I’d suggested doing the upgrade in-store, but they couldn’t guarantee I wouldn’t lose my data. I’d even thought of using a friend’s iMac, with a new user account, to perform the upgrade. There seem to be so many potential pitfalls that I’ve decided to delay upgrading until I get home. Pity, because I cannot report on my first impressions of iOS4.