Hi Rick,
If you are manually drawing the 2d elevation (not a 3d model), it would be better if those lines below ground level actually used a dashed linetype, not a coverfill. Also note that white pens are automatically converted to black (and vice versa) in Autocad to ensure they contrast against the background! This would not look good with a coverfill!
Autocad interprets and displays fills 'fairly' well, but my version (LT 2004
) cannot replicate fills from ArchiCAD, it comes up with a 'cannot find pattern' error. I don't know if this is solvable. I know AC12 has more fill conversion options in the dwg translator than AC11, but I haven't tried them yet.
You are more than welcome to email me an extract of the drawing in dwg format and I can email back some screenshots in Autocad if it helps. PM me if you're interested. You also may be able to find a free downloadable dwg viewer from Autodesk, but I'm not sure if there is a Mac version available.
Also note that you can use ArchiCAD to view dwgs directly, which will give you an 'indication' of what it may look like in Autocad. Funnily enough, ArchiCAD does a slightly neater job of interpreting its own dwgs!