It does have the evaporative cooling negative of... evapouration, this may or may not matter to you.(it would matter to me)
You say "mist" and I think, how powerful is your pump, obviously if you plan to have such high pressure spray nozzles that it makes a mist, you will need quite a bit of pump power to do it.
If you don't have quite the mist, I don't think the water will cool very well in such a short distance. Just look at people's WCing bongs, usually quite tall.
If you're dead set on ghetto, you can still use a closed loop solution by making a ghetto radiator or sorts, but if you wanna see one of the best looking Evap. Cooling Solutions I have seen check out Volenti's work here (wow I'm gonna use the search function now... wish me luck):
http://forums.procooling.com/vbb/sho...&threadid=4469
And while I was searching... Volenti came up big again:
http://forums.procooling.com/vbb/sho...&threadid=6057
Just some ideas o what has been done out there. GL