This THREAD at AUGI elicited a useful bit of information, like many do. Steve Faust writes in response to a post that Revit is exporting dwg text poorly.
"It's an option in ACAD to have "Background Masking" which is essentially the same as opaque text in Revit. Revit is trying to keep the export looking the same as your Revit drawing as much as possible. If you want opaque text in Revit but not in CAD, you'll need to open the Autocad drawing, use Quick Select to grab all the mtext, and turn off background masking in the properties panel."
This is a screen capture of the topic in AutoCAD 2009's help documentation:
Thanks Mr. Faust!