From what I've read, seeing a rattler at 9,000 feet is unusual.
I've come across four in my travels through the Sierra - all between 5,600 and 6,800 feet. About ten years ago, we ran into one (not literally, fortunately) crossing the trail about halfway between Little Yosemite Valley and Half Dome.
Part of me gets a thrill each time I see one out there, but I think I prefer my encounters with bears.