Can "drunk" be used as a noun? [closed]

I was reading Post Office and the very first sentence looked a little off to me

"It was Christmas season and I learned from the drunk up the hill, who did the trick every Christmas, that they would hire damned near anybody, and so I went and the next thing I knew I had this leather sack on my back and was hiking around at my leisure."

What I did understand from the sentence is that he got to know about the job from a drunkard. Am I correct?

If anyone has read read the novel or the author before. I wanted to ask this regarding the novel: The tone in general of the novel is very informal and conversational. I wanted to know how popular is this way of speaking. Is it specific to certain states in US or it is more of a nationwide phenomenon? The author seems to be brought up near Ohio and California.

I'll speak from my experience (middle-aged male, living primarily in the northeastern U.S., Chicago, and briefly in Los Angeles, as well as communicating with people around the country): "drunk" is by far the more common noun. To my ear, "drunkard" has an old and formal feeling to it.