Hiya, I'll try to keep this short, and to the point. I recently stumbled upon a way to enter Wintergrasp, with no flying mount involved, nor the portal in Dalaran.
It's extremely simple, merely run along the edges in Icemist village (Dragonblight). There's a spot around 22.53, 42.98.
From here, merely walk forward, and you will notice that your zone changed to Wintergrasp.
Now, from here, pull one of the mobs over to this area, and let them kill you.
After you die, you'll res at one of the Wintergrasp graveyards. I forgot to screenshot when I rezzed, and I don't feel like dieing again, but it's pretty self explanatory.
On a final note, I'm well aware that this is really basic, and simple. I wouldn't be surprised if it's already been posted before (however, nothing came up via search).