Careful guys, I work for Autodesk.
But really, AutoCAD can be a struggle to get started with...
Have you tried AutoCAD WS? It's web based, and it's free:
Try out Eagle, DesignWorks Lite, McCad or SolveElec. Or if you can compile software, try xcircuit, though it's got a bigger learning curve. Fink has a builder for it too if you know Fink.
I'll second ExpressPCB. I've seen tube symbols posted for ExpressPCB. My biggest complaint about ExpressPCB is the "undo" is only one deep.
A second choice would be LTSpice. There are tube symbols posted on the Web for LTSpice too. I just make my own. LTSpice is just one huge drafting page.