I would suggest that you try DraftSight:
http://www.3ds.com/products/draftsig...ad-draftsight/
It is cross platform compatible.
I have it installed on Windows Vista on my computer at work, and on Ubuntu Natty on my laptop at home.
I have had success opening Autocad files from even the latest versions.
If you are familiar with Autocad then you should be able to find your way around the program with a minimal learning curve.
Cheers!
Sonny