Although GPG supports strong encryption, it can only protect privacy when applied correctly. Particularly, the private key and the passphrase must be protected. This sounds pretty easy, but it is not, especially when GPG is to be used on a computer managed by another party.
A computer that is managed by another party can grab a passphrase by means of hardware or software key logging. Furthermore, as soon as the private key ring is exposed to the file system of the computer managed by a third party, the file can be copied.
In other words, do not use GPG to decipher files on a computer that is managed by a third party. Unless you have full administrative rights and confidence about the security of a computer, do not expose your GPG private key or passphrase.
What if you need to decipher files or messages sent to you on-the-go? I would not put the private key file on a thumb drive and rely on computers in a hotel. Instead, bring your own computer and use that for deciphering.