In iOS 7, the document directory of the iOS simulators can be found in:
/Users/Sabo/Library/Application Support/iPhone Simulator/
However,
If your app uses CoreData, a nifty trick is to search for the name of the sqlite file using terminal.
find ~ -name my_app_db_name.sqlite
The results will list the full file paths to any simulators that have run your app.
I really wish Apple would just add a button to the iOS Simulator file menu like "Reveal Documents folder in Finder".