best transportation from regal riverside hotel to yuen long in HK

I think the local MTR is the best method to Yuen Long.
From your hotel, you can easily walk to Sha Tin Station to take the East Rail Line to Kowloon Tong Station and then change to Kwun Tong Line to Prince Edward Station. Then change to line Tsuen Wan Line to Mei Foo Station. Then change to West Rail Line to Yuen Long Station easily.