[UbuntuGnome] trying to boot into grub with full disk encryption

I've got a fresh install of Ubuntu-Gnome 16.04 and I've updated all the software. I selected full disk encryption when I installed Ubuntu. I'm using a Dell Inspiron 17R with a 500GB hard drive.

I've had some video issues with flickering. I was reading about a possible fix here:
http://askubuntu.com/questions/76093...vidia-graphics

When I try to enter a TTY with ctrl-alt-F1 my screen goes black and the laptop reboots. The solution at the page above is to first boot into GRUB.

The full disk encryption prompts me for the decrypt password when I reboot or boot up. I'm trying to boot into GRUB but pressing shift before the descrypt prompt or after the decrypt prompt doesn't get me to the GRUB menu.

I am guessing I'm doing something wrong. Anyone have any suggestions?

I would be grateful. Thank you.