Ran into the same issue with xubuntu 13.04. The old way many online docos referred to (via Settings > Keyboard > Layout Options) no longer worked because there was no such button any more. Here is the new conventional (as in, no shell commands or X11 conf editing required) method that worked for me, in detail:
- Make sure the xfce4-xkb-plugin package has been installed (normally it should).
- Right-click on the top panel and select Panel > Add New Items...
- Select the Keyboard Layouts item from the list. A flag icon will appear in the panel.
- Now right-click on the flag icon in the top panel and select Properties.
- Now you will get the actual layout switch setup menu where you can choose your layout change key combo as well as customize other useful stuff including the list of layouts.
P.S. I don't mind using the shell or editing the X11 configuration. For that matter, I love using the shell. However, I hate it when the shell needs to be used to set up a GUI. :)