The U.S.English (us) layout on my machine has a Dvorak "Layout variant" already, so you just need an easy way to switch between it and the regular layout.

The KDE Control Center --> R&A --> Keyboard Layout menu has a drop-down menu for this purpose, or you could just use a one line shell script similar to SWMBO's to do it, without having to navigate all those menus.

I'm running KDE 3.5, which is newer than the stock Breezy KDE.
You also could upgrade to KDE-3.5 on Breezy, by adding this line to /etc/apt/sources.list:

deb http://kubuntu.org/packages/kde35 breezy main

And then do apt-get update ; apt-get dist-upgrade to fetch/install it.

Cheers