NJ Hiker, you didn't indicate how long a period you were looking at, but in the immediate area around Whitney your choices are pretty much car camping at the Portal (8300') or Horseshoe Meadow (10K'). If the Rock Creek property you're referring to is the one in Mammoth, that's about the closest elevation+comfort option.
Something new my family and I tried last year was renting a condo in Mammoth Lakes, which can be had quite cheaply since summer is their off season - well less than $100 per night in many cases. We spent 5 nights in Mammoth, dayhiking the numerous trails in the area, including Yosemite and White Mountain. In Mammoth, you get the benefit of sleeping at close to 8000 feet, which was key to me since the previous year I failed to summit Whitney due to AMS at 13,000 feet - caused almost certainly by never sleeping above 3700 feet the entire trip.
Between that overnight acclimation in Mammoth and dayhiking up to 12,000 feet, I was well prepared for Whitney. The day after leaving Mammoth Lakes I was signing the Whitney summit register with no AMS symptoms at all.
Non-camping alternatives at elevation in the eastern Sierra are slim pickings. We went this route rather than attempting to ship a family's worth of camping gear across the country and back. This coming summer will be our third "annual" trip out there and, unless a better idea pops up, we'll probably do roughly the same thing.
