Wondering how many days in advance I can start with frosting a cake and starting to decorate it? Also its going to be like 90 this weekend when the cake is due should I put it in the refridge before I go?

thanks

I personally do not make cakes more than 3 days before delivery (generally for me 1-2 days though)... for optimal freshness... as far as heat... it really depends on your buttercream recipe and what its melting temp is at. Also will the cake be outdoors? shaded? direct sunlight?
With buttercream you really want to keep it shaded, even with the best (highest temp) buttercreams.

From experience - I only do buttercream cakes (fondant for decor only) and have never had a problem. I even had one cake that had to sit in a non-air conditioned vehicle (with the windows down) in a closed box (no sunlight) in 80degree weather(so in a car = hotter) for 2 hours and it didn't melt at all.

No this for putting it in the fridge... sometimes when buttercream thaws, colors "can" run into each other slightly.

I have never put a buttercream cake in the fridge, simply for other reasons but was advised once of the "color running" possibility.

If you take anything out of the fridge into a hot humid environment, condensation will develop on it. I wold just keep the cake at room temp.