How do I make driven dimensions come in as fractions?
So you want driving dimensions to display as decimal and driven dimensions as fractions? You can click on the driven dimension (or Ctrl select multiple dimensions) to highlight it, click on the Other tab in the CommandManager, click in the box for "Override Units", and choose "Decimal", but I don't believe there is any way to do it automatically, short of a macro.
Click in the box in the Length row and the More column (upper right). Do you have the box checked for "Round to nearest fraction"?