Buy a gryphon ride from the gryphon master Thor, then bring Lewis' Note to Osric Strang, in the shop Limited Immunity, in the Old Town of Stormwind.
For a small fee, you can take a gryphon to Stormwind, so you can deliver Lewis' note to Osric. You won't get there faster any other way.
If that sounds acceptable, then just speak to me again when you're ready for the ride. I'll charge you a little, but trust me; it'll be worth it!