Yes but there is a little quirk. In the wow video settings choose windowed maximized rather than fullscreen. If you choose fullscreen it will black out the 2nd monitor.
This has the semi-unfortunate side affect of making the menu bar appear when your cursor hits the top of the screen.
Additionally, I have noticed that sometimes when switching from the 2nd monitor back to wow, wow may have trouble regaining focus (I think usually when i click on wow with other than the left mouse button), this is fixed by selecting the wow icon from the dock.