What is the drive up and down big bear like?

I drive a Honda Accord 2006 (automatic), I'll be leaving tomorrow morning/afternoon from Irvine. My car has D-D3-D2-and D1 which one should I drive on while going up and down the mountain? I'm a bit concerned about driving down the mountains, I've heard a lot of scary stories. Any tips or recommendations would be great!

Its kinda like little bear… But bigger.