Ponzy,
I'll be your friend on 23rd July. I also will be doing the day hike then. Furthermore, I'm also from the area where I don't have access to higher altitude practice hike.
My plan is to go to Lone Pine on 20th and spend the couple of days before the "big one" in the area.
Currently, my training is three fold - every day I run 4 to 5 miles in our neighborhood (which is quite up and down), every other weekend I spend 2 to 3 hours on treadmill at 15 degree incline at around 2.5 to 3 mph, and every other weekend I do an endurance hike in Appalachian mountains in TN area. This hike could be up to 20/26 miles and so far I found out that I can finish it in 10-12 hours.
This is the training that I self-prescribed and I'd welcome some suggestions from experts if I should change anything.