I have created a bootable usb of ubuntu 14 and I know it works because it works on another laptop. I just received an Asus zenbook UX31A with windows 8 on it. I disabled quick boot and secure boot in the bios menu (newest Bios). when I attempt to boot from the USB, it boots straight into windows with no dialogue of any kind.
Hardware: Asus Zenbook UX31A
Ubuntu: 14.04
Dual-boot: Windows 8