As the title says, I would like to be able to install Ubuntu on a USB stick such that I can (a) boot from the USB stick and (b) Ubuntu uses full disk encryption. I was able to put Ubuntu on a USB stick using Linux Live USB Creator, but it never gives me any install options (install options in the boot menu appear to be for installing Ubuntu on the machine itself, not the USB).
unplug, disconnect or otherwise disable the internal drive
boot into one USB stick,
install Ubuntu into another USB stick (a fast USB 3 stick or SSD connected via USB)
in the installer's partitioning window, use the option 'LVM with LUKS encrytion'
The following link and links from it can help you with details,
back up your data before start ! check this link luks encryptation usb *this was tested with Ubuntu 12.04.