Funny you should ask, I just finished playing through that level 2 days ago!
***** SPOILER ALERT! *****Neway, follow him and be sure to go to the corner of the 'quiet zone' from where he stops as you can pick up some air foil and sticky shocker rounds. Save your ammo and just sneak behind the policeman, grab him, take him to a dark corner and KO him. Or if you prefer, as soon as you get the extra ammo head for the exit (the way you came in) and avoid the officer all together.
As you head back out of the 'quiet zone', turn right at the intersection (you previously came from the left) then left at the next corner. Rush about 1/2 way down and hide on the left in the dark until a women passes by you, then continue on. At the next turn, stay on the left and go all the way down and wait right next to the policeman until they move away. Follow them while staying out of view (or dispatch them one at at time, quietly, and hide the bodies).
Your goal is at the end of this street where you turn left, find a pole and climb to the roofs. At the end of this will be a zip line, climb down after 'zipping' and talk to Dahlia Tal through the wooden fence. She will then open the gate for you to follow her.
