This is a difficult map to explain, so I use cardinal directions; pause your game, view the map, up=N, left=W, down=S, right=E.
Start in the SW corner. Look at the cop car in the corner. Jump on the mattress, onto barrel, onto cop car, get on the trunk of the car and jump onto the wooden balcony. Here you can snipe out from the laundry. You can get on the railing and jump onto the black fridge and up onto a skinny ledge in front of the yellow section of wall (you are a sitting duck up here, stay behind the laundry).
Next, look from there at the small shack with skull posters on the side facing you. Near that is a yellowish barrel, jump on barrel, jump onto roof of that shack. This overlooks anyone coming up those stairs.
Heading north, you will see a dumpster on your right, climb dumpster, climb roof. From here you can jump down onto a ledge that crosses the ravine (flood channel?) and get you to the southern building.
From the building that you got on from the dumpster, look north and jump to the small red building (you can also climb a dumpster behind this building to get up here).
Head to the north face of the small red building, jump north to a small grey building with small roof extending out from it. Climb inside up there.
Jump out of the grey building and head east across the small bridge. Look left down the ravine and jump onto a small ledge (2 inches wide) along the right side of the ravine. This will take you to the north face of the map overlooking the area by the explodable tank there.
Make a right, you are heading past one of the bomb sites in SnD. There is a small room there, you can get above it on the yellow rail and jump on top of that doorway (not good for much).
Heading east along the north face, you will pass the trains on your left, and get to the broken cement wall. Get on the right section and you can climb onto the blue container. There is also a yellow car next to the blue container, climb that to get on top as well.
Heading south now along the eastern edge, there is a space between the containers with a lot of grass to hide in (under the overpass).
Just past that you will come to another broken cement wall with an explodable tank to your right. Jump onto the lower wall, jump onto the higher wall, jump onto the explodable tank. You can also climb the stairs behind the wall and jump from the railing onto the higher wall by the tank.
Go up those stairs and inside that building. Look left at a window there. You can climb in through the window from the outside. Continue through that building, you will go through a door and there will be windows to snipe from. In the middle of that building is a tank, climb the tank, climb up onto the catwalk (bear there), climb onto the crossbeams and/or drop onto a small tank below.
Head out the bottom door and go 5 feet into the next building (SE corner with parking lot behind it).
Walk west out of that building and turn around to face the building. You will see a low cement wall to the left of the main doors. Get on the lower end, jump to the higher end, jump onto the top of the door, climb in upstairs window (this is one of the best things to know in SnD games, nobody expects it).
Go back to the starting point in the SW corner. Go through the doorway on the south side. Go upstairs and follow it to the end. You can jump off onto a small browm ledge in front of the shack there or you can jump onto a 1 inch wide ledge on the side of the brown shack.
The last place to discuss is the group of connected buildings in the middle south; on one of the southern sides is a ladder to climb up top. This is one of 4 ways up there. The other 3 are from the north face of that building. Find the column thast has the ladder on the side; climb that ladder, get on the rail up top, jump onto the roof. From the north face; jump onto the yellow car, jump onto roof. From the north face, go to the tree, jump onto the boxes there and climb up and onto the low roof.
Go to the southern end of this building, on the eastern face is a small building below you, drop onto the ledge to get inside that small shack.
I hope that was all clear enough to understand.
[more cheats for Call of Duty: Modern Warfare 2 here]