The long term parking at the portal has worked for me, up in the trees, or in the overflow lot. Make sure your car is clean (no food or other intersting smells) and nothing you can see through the windows would interest a bear or human critter. So no French Fries under the seat, no spilled burger juice in the seat fabric, etc
Same is true for long term parking at Tuolumne Meadows. I've left it there the last three summers. I never felt good about leaving my car on the lot near Curry Village down in Yosemite Valley (hot, dusty, too many people, and you need a permit sticker on it, so no car cover)