That's a really bad idea, especially if you're not a US citizen. If they want to access your computer, they _will_ call your superior back home and might tell him that they will either get the password or deny you entry.
I think they'd just threaten to keep the laptop instead. Once they've taken the laptop from you, presuming that's the only reason they're stopping you, they should no longer have cause to prevent you from continuing.
Why would they threaten that? An encrypted laptop would be useless to them without the password. The worst they could threaten you with is denied entry or detainment, so I think it's far more likely that they would threaten with that to compel you to produce the password.
In any case, if you are worried about protecting your data, you put yourself in a pretty bad situation if you rely on encrypting that data and hide the password. Bringing a relatively clean laptop will just avoid the issue altogether and will allow you to be cooperative with them.
Remember that they don't _need_ any cause to deny you entry or detain you, as long as you're not a US citizen.
