For how long do you need it to keep? Is your home Air Conditioned?
If only for a day, I think it will be OK. But it really depends on your recipes, and the ratio of sugar to dairy. I don't know the science, but I've read about it.
If it were my cake, I'd keep it out, but make sure the A/C was on.
Here's a handy safe storage chart for frostings and fillings:
http://tinyurl.com/ymqp6x
(From Sarah Phillips of baking911.com.)
Also, here's a discussion (with recipes) on how a determination is made regarding the need to refrigerate, or not:
http://tinyurl.com/2ydx9b
(From Sarah Phillips of baking911.com.)
HTH
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