Language is something that evolves with time and trend. I'm just saying, as an ethnically Chinese person whose mother tongue is Chinese, the mythical figure was not the thing I think of when I first saw the word.
Salad is still used to in the media and the mainstream to mean as a type of food. While the word "牛郎" is whole different matter.
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As a Cantonese speaker, the mythological meaning of 牛郎 is the first one that comes to my mind. Outside of its mythological context, I can only see the word refer to male prostitutes in Japan and maybe Taiwan.
According to this Wiktionary page, every Chinese-speaking region has its own euphemism for "male prostitute", with only Taiwan using 牛郎: https://en.wiktionary.org/wiki/%E7%89%9B%E9%83%8E