I know you should have them set to the most "float". Each pedal system has it's own means of adjustment. I have Speedplay Frogs where you just twist out of them. I have never fallen, even twice when I had to "emergency" stop.

One way to prevent falling is to unclip WAY before you have to stop. I am in this habit now. Sometimes I am even cranking with the arch of my shoe on the pedals, but I am unclipped and ready to put my feet down.