Haven't heard anything recent about DHL, but last I heard it was a problem area. Before 9/11 I was told by other spotters it's only good on weekends; during the week DHL employees actually need the lot.
I was at the Northwest Cargo lot for a couple hours last Friday, no problems. You don't need a ladder there to shoot approach shots if your timing is right, and try standing towards the middle of the lot rather than close to the fence.
I did pull my ladder out to shoot a Southern Air Cargo 747 as it taxied onto 25L, no problems but I put it back in my car's trunk as soon as I was done.
David / SAN