There is an easy way to do this, both in Claris CAD 1.0 and in MacDraw II.
1. Select "Rulers..." from the Layout Menu
2. Deselect "Show Unit Name"
Any dimensions you create from then on will not show unit names.
In Claris CAD 2.0 this option has been placed on the Dimension Floater. Select "Show Dimensions" from the layout menu to access this option.