Spirit Vision Photography Loc: Behind a Camera.

When I was a hardcore climber/photographer, I spent a lot of time in the Valley, climbing and shooting. I never needed anything longer than a 200mm. And used my wide angle the most often. Travel light. Also, Yosemite has a great shuttle system.

Architect1776 Loc: In my mind

I seriously doubt the OP will be cliff climbing.
When I was jumping out of planes and helicopters I found the little Kodak disk camera was perfect to fit in my hat. But going as a civilian to various places like this or the Grand Canyon I will always take my 100-400mm and use it a lot. I easily spot deer, elk, birds etc. That the average Joe misses.
It is invaluable to have 400mm+ with you in places like this.

augieg27 Loc: Central California

Nikon 18-200mm, that's all I used when went to Yosemite last year.
Even in a crop sensor is wide enough and the long reach (300mm) is plenty for me.

DJphoto Loc: SF Bay Area

Traveling light is a good thing. I've been to Yosemite several times, and if I was going to bring one lens, it would be my EF-S 18-135 and I would likely use it for about 90% of my photos, next would be the EF-S 10-18 for the wide shots, then it would be my EF 70-300 which might not get out of my bag.