Unless you need to cut the cake in layers, there is really no need to defrost, you can decorate although it is very cold or frozen.. OR let it sit on the counter for maybe 1 1/2 hours.. cake thaw very quickly, not like meat.. 
If you don't need the cake until tonight, it should be okay by then.
I've taken cake out of the freezer around 10 a.m. and it was thawed by 3 or 4 p.m.
Just depends on the temp of the room. I have also put my frozen cakes on a heavy jellyroll pan, still wrapped, and sat them on the stove TOP with the oven on just enough to warm the stove top. I've never put them IN the oven.
Ok...so the microwave is OUT! lol 
I need to take the cake to class already iced...so that's why I wanted to speed up the process a little bit. I like your idea, LittleBigMomma, about turning the oven on and sitting them on a sheet pan on top of the stove. I think I'll give that a try! Thank you all soooo much! 
You are welcome!
Just "flip" the cake every once in awhile and don't let the stove top get hot.
Good luck and have fun tonight at class!
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