How can I change the font used on a site navigation bar

You can alter the font applied to a site navigation bar without ungrouping the bar.

Editing the text on a site navigation bar

• Using the selector tool, click once on the site navigation bar.  The status line will read '1 navigation bar on 2 layers'
• Switch to the Text tool causing the 'Text Tool Infobar to display'
• Alter the font and its properties as required.

Editing the text applied to sub menus

• Using the selector tool, double click on a site navigation bar to open the Navigation bar properties dialog
• Click on the button labelled 'menu style...'
• Alter the font and its properties as required