In order to get to Salem from Yercaud, you need to get to Cherry road from State Highway 188. You then need to continue on Cherry road till you reach your destination.
Salem is to the south of India and this part is known to have very hot summers. The temperature in Salem during the months of March to May can go up to 38 degree Celsius. This makes it difficult for you to travel. This city also receives heavy rainfall so if you are planning a trip to Salem during the monsoons make sure you rent an air conditioned cab to travel in comfort. Winters are ideally the best time to come to Salem because the temperatures here don't drop too much and it is a pleasant time to move around.
There are no known alternate routes from Yercaud to Salem. You need to take the route via State Highway 188 in order to reach Salem in an hour.
The road conditions between Yercaud and Salem are quite comfortable and you will be able to travel without any problems.