If you are visiting the USPTO, do not bring a “personal removable media storage device.” U.S. Gov’t computer security has been compromised on numerous occasions based via USB drive viruses. The solution is to email the file to the examiner (and yourself); bring in a “finalized CD/DVD“; or connect via a secure file sharing service (PTO suggests Kiteworks).
The prohibition is written broadly — prohibiting anyone from entering the with “devices that can operate as removable media storage devices (e.g. PDAs, digital cameras, and Apple iPods).” Presumably, this also includes your smart phone — I have contacted the PTO for clarification.
The PTO Notice indicates that most USPTO locations will include scanning-equipment “to check removable media for policy compliance.” However, that process will cause a delay in admittance (and invade the privacy of your device).