Most hanja with the reading Yong are pronounced that way in all dialects of Korean.
However, the character used to write the family name (龍, meaning "dragon"), is also read as Ryong and spelled as such in hangul (룡).
[1] In a study by the National Institute of the Korean Language based on a sample of year 2007 applications for South Korean passports, it was found that 97% of people with this surname chose to have it spelled it in Latin letters as Yong, while 3% chose to spell it Young, and none spelled it Ryong.
They identified with the following bon-gwan (the hometown of a clan lineage, not necessary the actual residence of the clan members):[3] People with this family name include: Yong is an element in some given names.
There are 24 hanja with the reading "yong" and one with the reading "ryong" on the South Korean government's official list of hanja which may be used in given names; common ones are listed in the table above.