Unless they have changed something recently, Tinkerbell only flies at night just before the fireworks, so you won't have a problem with the sun.
She flies between one of the turrets of the castle (on the side closest to Tomorrowland and the area near the Plaza Pavilion restaurant in Tomorrowland. I'm not sure of her exact landing location, but if you look up, you can see her path (don't tell anyone it's a wire).