I can't read the font in my chat frame or action buttons... can I change the font size?
Yes... no... and yes.
If the problem you are having is with your chat frame, then yes you can change the font size. Just mouse over the top left of the chat frame (or combat log) slightly above the frame until you see the "Settings" tab... you'll find and option there to choose a font size. You can use that to increase or decrease the size of your chat frame font.
If the problem you are having is with the text in your action buttons or debuffs, then the short answer is no, you can't change it. For now (until I rework the action buttons) the font size is tied to the button size and the only way to change the button size is to hand edit the layout file.
Which leads to the long answer... yes, you can change the font size if you really are adamant about it. Edit the file [ Interface > AddOns > nUI > Layouts > Default > nUI_Layout_Default_Dashboard.lua ] and locate the section "nUI_DefaultConfig.ButtonBars" which has subsections in it for every action bar nUI supports. Each one of those sections has a "btn_size =" option in it which controls how big the action bar buttons are on that bar... changing the button size will cause the font size to change proportionally with it. There is, however, a side effect... if you change the button size, then the whole bar gets bigger or smaller, and that means it doesn't fit in the space provided for it anymore, either.
What people don't get is that I am, ultimately, an artist at heart.
My brush has two colors, 1 and 0, and my canvas is made of silicon.