Changing default runlevel in Ubuntu...

-Edit /etc/init/rc-sysinit.conf using any of your favourite editor(mine is nano ;))
-Find env DEFAULT_RUNLEVEL which should be set as 2, by default.
-Change it to your desirable runlevel.
-Give a reboot and you are done!

Here is a quick reference

Debian Linux runlevels

ID	Description
0	Halt
1	Single-User mode
2-5	Full Multi-User with console logins and display manager if installed
6	Reboot