Can you use both QWERTY and Dvorak?
YES There are many who report efficiently switching between the two formats without issue. I personally choose not to. Since I know how to change the keyboard layout on all Windows and MAC machines I would rather add the Dvorak layout then use QWERTY.
The only situation where I don't switch the keyboard layout is when I am using a smartphone or an iPad without an external keyboard. In these cases I generally use the two thumb texting method.
How do I change my computer's Keyboard Layout?