One more thing...after you spray on Simple Green, use a toothbrush of some sort to get into the nooks and crannies of everything, and once it's dried off on it's own a little bit, start the engine and let the rest evaporate with the hood open, or you can use a leaf blower, but no matter what, let the car run after all's said and done.
I've tried it on a '92, with everything exposed, so I can vouch for the fact that your car won't die on you haha.
Still, do this at your own risk. Clean engine bays make it easier for mechanics, since they won't have to sludge around in grease and such while working.
This was a forum I used to be on for my first car (that's not my car below though), and a clean engine bay can honestly look quite nice.
92 Acura Legend
The citrus spray gives it a shine, whereas the Simple Green is just an engine degreaser.