train schedule and bus schedule from Yanan to Yulin

1. The buses are scheduled at 9:30, 11:00, 12:00, 14:30, 15:50, and 17:30. The trip takes about 4 hours. The fare is CNY 88.5.
2. The trains are scheduled at 12:11, 12:33, 14:52, 18:06, 18:56, 19:10, 20:39, 21:44, 01:11, 02:29, and 04:40. The trip takes about 4 hours. You need to pay CNY 41.5 for a hard seat; CNY 87.5 for a hard sleeper; CNY 132.5 for a soft sleeper.
So, you may choose the way that suits you. :)

For bus travel, as I know, many schedules are also available at the South Bus Station (opposite the Railway Station). I remember they drepart from 06:00 to 17:00. Just for your reference anyway!