Beantown, lots of people park their cars long-term at Whitney Portal. It should be ok there. In fact fewer thief types would visit there than Lone Pine.
Another option would be to park at Mammoth, and catch YARTS into Yosemite. That way you would have the option of riding the bus out of Reds Meadow midway through your hike, and using your car to pick up any resupply stuff you needed anywhere in Mammoth. You could then take the ESTA/Crest bus back there from Lone Pine after your hike. Forest Service people can tell you where there is parking, but I have parked along the road here. (
Gmap4 map) The Reds Meadow bus drops you off just west of the main parking lot.
