Change Fonts *Now* in Theme Manager
That's right you heard correct! This great gentlemen over at Miui-devs named "Endless Dissent" has taken on the challenge of making this work and has succeeded! And if your like me and was sick of trying different methods with little success (Font Changer) then check out this link
[FONTS] Theme Manager Fonts
All you have to do is download the font you want and drop in the Miui/Theme folder, go to the theme manager check "edit theme settings" scroll down to fonts and there should be the fonts with previews. Select your font reboot and enjoy :)
He will also take requests if your favorite font is not already converted. This is strictly for people who did not know, so if you already did ignore this post
Tip: Flash your font after you flash your theme as most themes flash the default font with them so, if you flash the font first, then the theme you will probley lose your custom font.