First, pick up Crocolisks in the City, the fishing daily from Old Man Barlo. There is a bug at the moment where the quest item is a 100% drop when fishing in Orgrimmar, and ALSO increases the chance for Old Crafty to drop.
Don't loot the Baby Croc until you loot Old Crafty.
There WILL be a confirmation box to loot Old Crafty, even if you are alone - so make sure you don't recast without clicking "Yes" to the loot!
Next, be prepared to die at least once or twice. FD and Shadowmeld don't work on Orgrimmar guards, so I would assume Vanish/Invis etc don't work either. I recommend mounting up and getting as far as you can through the back door of Orgrimmar (accessed via a bridge in NE Durotar going across the small river between the Barrens and Durotar), preferably sans armour.
The place I fished from is in the Valley of Spirits. The dangerous part about this is that this is where any portal to Orgrimmar dumps the Horde, so there's usually a bit of traffic. However, there is a place behind the rock and palm tree in the area where you can fish and be very hard to spot (unless Horde visit the priest trainer/cloth handin person).
Here's a screenshot of the rock/tree I'm talking about:
...and another view from behind the rock:
If you're on a particularly bloodthirsty server, you may want to stop fishing if Horde port in, so that they don't hear the splashing and come to investigate. When I did it, the Horde usually went straight out the front of the hut after porting in and didn't look back, so I didn't get bothered at all.
Unfortunately for Horde, this bug doesn't work for Ironforge because the fishing daily is for Stormwind... and it's a lot harder to get into IF than Orgrimmar. Sorry! :(