If you're looking for better roads to get into the Valley then like several have already said, head South and take 152 across. If you take 17 north then you're heading into Silicon Valley and the traffic and lots of freeway construction, especially on 580. Also that forces you to take 120 into Yosemite, which is a good road, but it is also the highest road going into the park from the west.
If you go back down and take 152 then you can pick up 140 and take 140 into the park. 140 follows along the Merced River right into Yosemite Valley.
