You can change it, you have to do it in the HTML.
You add a line in the section you want to change - body, wrapper, posts, etc
font:insertfont;
Or find that line in the section and change it from $bodyfont to the font name you want to use.
Or you can go up into the Variable definitions and find the one you want to edit such as "body font" and then change the default font from what is listed to what you want to use.
If you go with any of the standard windows fonts or those that come with common use programs odds are everyone will see the font you want to use.