I skied down from Trail Crest in January and again in March of 1993. It was pretty cool, but it was the limit of my ability. Down lower, it was dark, the snow was crusty, and we had heavy packs. It wasn’t much fun.
Eleven days ago, I hiked up the Mountaineers’ Route and down the main trail. There was a guy carrying skis up the Mountaineers’ Route. I never talked to him, but I’ll bet he had a super run from just below the notch to well below Lower Boy Scout Lake. (The chute is way above my ability, though.) I also think you could have had a great run from Trail Crest to about 9,500 on the trail.
Now for the bad news: by late May, there will be much less snow, which means you’ll have to carry your skis quite a bit. There will be sun cups, and, as Steve said, conditions below Trail Crest may be ice or slop. It might be possible to skin most of the way up to Trail Crest if the snow is perfect, but you’ll probably end up wearing crampons and carrying your skis.
Having said all of that, there are few pleasures in this life that can match skiing down past a bunch of people wearing boots and sinking into the soft snow.