Driving CA 120 from the west up the New Priest Grade.

It's windy because it's grade is a half of that of the Old Priest Grade.
http://www.pinemountainlake.com/Page/21389~335619/ErrorNotFoundhttpwwwpinemountainlakecom80Priest-Grade-Grizzly-Gulch

You should be OK since the alternative Hwy to get to groveland is many miles further. 120 is indeed steep and windy but it is doable. Because it is steep and has tight turns you won't have to obtain a lot of speed. one thing that I find helpful going up east is you or your co pilot can look up the mountain and see the traffic coming down. That gives you a heads up on when you might meet that vehicle coming around a turn. Take your time around those tight turns and try to keep in your lane and you should be OK.