Here are some distances for you from Google maps. These are distances from Downtown South Lake Tahoe to the Yosemite Valley.
Taking 50 to 395 and then over Tioga Pass: 201 miles
50 West to Highway 49 to 120: 204 miles
50 to 99 to 120: 269 miles
And actually after looking at the map again, I just realized an even better route and that is to take 89 out of South Lake Tahoe to 88. Then take 88 down to 49 and 49 to Highway 120. 88 is a nice scenic route and usually has very little traffic. Also by taking 88 to 49 you miss some of the most windy parts of 49 which is the section between 50 and 88. And this route is only 200 miles, which is even shorter than Tioga Pass. Just remember this to Yosemite Valley. If your actual destination is over by Groveland then this would be by far the best route.