On/off or yes/no conditional help, please.

I'm trying to set a simple conditional to allow my members to enable/disable a sidebar based on usergroup permissions.

I have a CPF (field18), Single-Selection Radio Buttons, with the options being "Yes" and "No".

In the user's profile options page, is an option: "Display the sidebar? (o) Yes ( ) No".

If the YES button is checked, I want a conditional to display the respective code. From what I can tell by hunting around vb.com, this should work:

<if condition="$post[field18] == 'Yes'">

But it doesn't. :\

What would the proper yes/no (or on/off) conditional syntax be?

Thanks!