I had no idea what this meant when I heard it. And I've certainly never seen this word in a textbook. I imagine I never will.
Anyway, all of that aside, let's get to the bottom of this phrase.
Fodonga, or fodongo, basically means to be lazy, messy, have an unkept appearance, or perhaps just a slob. In English we might say someone looks a mess, in public or private. A woman who goes to the store with hair rollers in place, maybe even wearing her bathrobe. The guy who goes out in public looking like he hasn't combed his hair in weeks and is wearing the most wrinkled t-shirt and pants you've ever seen. Those are good examples of fodongos.
And if you've ever seen any of the 'people in Wal-Mart' emails, you definitely know what fodongo means.
But if you still have some doubts about what 'un fodongo' might look like, I think this photo will give you a good idea:
So if you tell someone...
Estoy de fodonga
That's means you're looking a hot mess right now and have yet to spruce yourself up. Hopefully you're just sitting around the house, and not out in public.
Have fun with this one, you can get a lot laughs with it as you and your friends make fun of the crazy looking people you see in Wal-Mart!
¡Hasta la próxima!