You could:

1) When you install as beginner style or debian style, you will always presented with KDM log in screen. There is a menu button where you can select what type of windows manager you wan to log to. Choose boot to konsole.

2) Edit your /etc/inittab file. Go to KDE-->system--->file manager-super user mode-->open that /etc/inittab file.
On top of that file there's a line :
# The default runlevel.
id:5:initdefault:

Change id:5:initdefault to id:3:initdefault
Save and reboot, you will be presented with command line.
After you install nvidia driver, you need to set back your /etc/inittab to its original state..
Before you try install nvidia driver, I would suggest you search and read post about how to install nvidia driver in this forum.