Decrease GRUB timeout

The GRUB timeout is 8 seconds. Can this be turned down to 2 or 3 seconds? What is the best way to do this?

Try

sudo nano /etc/default/grub

change the GRUB_TIMEOUT value to 2 or 3

save

sudo update-grub

Not sure if I have a complete answer as I have a few more questions.

First - Permissions: you would normally need sudo to edit grub.cfg. If I'm editing from the commandline, I like nano, which is installed by default, so I would use

$ sudo nano /boot/grub/grub.cfg

If you haven't used nano before, once you're done editing use Ctl-O (the letter) to save and then Ctl-X to exit (the Ctl-O is optional, Ctl-X will prompt if there were changes)

Second - Grub: Editing /boot/grub/grub.cfg is probably not the way to go. Grub2 uses the file /etc/default/grub to get all its options and then generates grub.cfg for you. This is important, because grub.cfg gets updated when there's a kernel update or other things that might affect grub. So if you want your changes to stick you need to edit /etc/default/grub.

$ sudo nano /etc/default/grub
$ sudo update-grub2

More on grub here: https://help.ubuntu.com/community/Grub2/

REMEMBER TO MAKE A BACKUP BEFORE YOU CHANGE SYSTEM FILES :D

Third - 10s wait: I'm not actually sure that grub is your villain here, but hopefully the above will help you figure out if it is. Alternatively, can you elaborate a little more. Are you in the grub menu when you "select Ubuntu to boot?" what happens once you've selected it? Or are you referring to the grub picking a default OS - in that case /etc/default/grub will help.

A GUI method is to install StartUpManager:

$ sudo apt-get install startupmanager

You can set the Grub2 timeout using this utility.