The portable version of TrueCrypt as presented here always requires Admin privileges. The full information about TrueCrypt Traveler mode can be found here in the section Traveler Mode, yet my suggested way of setting up USB Flash Drive encryption should meet the need of most users:
Download, install and open True Crypt. Go to Tools, Traveler Disk Setup. Hit the Browse Button and navigate to your USB Flash Drive; click OK. Set AutoRun Configuration (autorun.inf) upon insertion of traveler disk to Start TrueCrypt.
Leave Include TrueCrypt Volume Creation Wizard ticked and hit Create. Click the OK button when you see the message TrueCrypt Traveler Disk has been successfully created. Click Close. Exit True Crypt.
Open the TrueCrypt.exe on the USB drive. Select Create Volume, then create an encrypted file container. Click Next.
Select Standard TrueCrypt Volume, then click Next. Select File and navigate to your USB flash drive. Name your container (e.g. USBcontainer). Click Save. Click 2 x Next.
Assign the amount free space you want to allocate to USBcontainer. Then click Next to enter and confirm a password.
Click Next. Click Yes if you see a warning message (or No and define a password of at least 20 chars).Click Format.
When you see the message The TrueCrypt Volume has been successfully created click OK. Click Exit.
Upon inserting the USB stick on another computer either Autorun comes up or you have to run Truecrypt.exe from the USB Flash Drive.
Hit Select File (USBcontainer), Click Open. Select a Drive letter for USBcontainer or click Auto-Mount Devices. Enter your password.
That's it, but do yourself a favour and learn or how to use TrueCrypt or the the portable version of TrueCrypt before you go 'live' !
