See everyone is different, I can eat cool whip by the carton. So can my dad, we LOVE it. Actually so do 8/10 people I work with. Our director bakes us cakes and angel food is popular request. Maybe it is a Texas thing. 
I don't see why you couldn't sweeten plain yogurt.
I have good luck with the Duncan Hines Angel Food mix myself.
Amanda
2011 Specialized Epic Comp 29er | Specialized Phenom | "Marie Laveau"
2007 Cannondale Synapse Carbon Road | Selle Italia Lady Gel Flow | "Miranda"
You don't have to be great to get started, but you do have to get started to be great. -Lee J. Colan