ej,
If you're doing Whitney on the 18th, I strongly suggest you give Gorgonio a shot. I'm just being conservative and giving you the full disclosure. It is doable without crampons, just not easy. More than half your hike will be without snow.
It will give you a very good indication as to whether you're ready for Whitney. Remember that you're gaining about a 1,000 more feet for Whitney via the main trail, and also covering about another 4-6 miles.
If you're not comfortable with the snow level on Gorgonio at 11,500, don't even attempt Whitney and go up that main chute or the traverse from the backside.
Oh, there's a few big fallen trees that you'll have to climb over or crawl under...it'll make your trip feel more adventurous.
