Try this:
- From Preferences, search for "text Font", and you should arrive at "General-Appearance-Colors and Fonts".
- Click "Colors and Fonts" on left if it's not already hightlighted.
- On the right, expand the "Basic" Folder, and double click "Text Font".
This is the default setting that the text editors and console use. It won't change the package explorer or other eclipse widgets.
While you're there, you may be interested in trying out this font. I find it to be much more readable: http://levien.com/type/myfonts/inconsolata.html