That's from Forgotten Realms Adventures. I feel like at some point Ed wrote a few columns about Saerloon but nothing is directly coming to mind. All I could find was the Melvos Hammerstars series, starting here: http://archive.wizards.com/default.asp?x=dnd/rl/20050216a
OMG Arivia, thank you SO MUCH! I was unaware of this product, I am sure to use it a lot. The map [in the PDF] is better but not by much; I messaged Markustay to see what he's got. Thank you both!