CA Central Valley

If your ultimate destination is Tehachapi I'd take 99. Otherwise you have to cut across to 99 from 5 down near Bakersfield. As already stated, both 5 and 99 are undergoing some major construction projects. Both are torn up through Stockton and 99 is bad through Modesto. A lot of the construction is being done at night so don't think you'll avoid it by going through at night.

Both 99 and 5 have had a lot of repairs over the last couple of years so I don't think there is much difference between the two as far as condition. You'll find bad sections on both.