Don't know you, so I can't say that under 10 hours is a dream or not. Give us your time on a trail on San Jacinto or Baldy and that'll give everyone a better idea of your health and whether a sub-10 is possible.
The trail is not hard to find at night. Don't stress about it. Since you're going to be up there for a few days, go up the trail to scout it out during the day. No permits needed until you get to Lone Pine Lake. Everything after that is even easier to spot. You'll get to know the trail better while acclimating.
It looks like there's going to be a lot of people up Skyline next Saturday.
http://www.mtsanjacinto.info/viewtopic.php?t=3526If you can get to the tram, you'll be fine for Whitney. If you can do the whole Cactus to the Clouds, you'll be golden for Whitney. If you can breeze up there, you'll have no problem with your sub-10 hour time.
Be VERY CAREFUL with Skyline!!! It's getting hot, and people have died coming down after giving up due to heat strokes. I'd carry at least a gallon of water if I was you. Read about the hike carefully before attempting. Good luck.
