When your're in Death Toll there should be a bulding where you usually turn on the crane and the zombies come.

You just go straight from the crane and the building is there. Jump then turn halfway at the same time then have sombody help you up and you should be floating.

If you want to go to the secret alleyway you just walk off the egde. You will fall but you shouldn't die.

Then walk on the side of the building till you hit the egde. So then take your pills and walk off the egde and there should be an alleyway where no zombies can get you.

This may take a few tries.