What’s the best recommendation for people drinking in the alley behind my apartment until 12 AM or later?? Is that considered public intoxication??

Yes, try to get video/picture evidence of them in the act and you can have them prosecuted by showing the police

If there homeless it's hard to get a complaint against them . Since they dont have an address they dont have anywhere for the ticket, summons, ect to be sent. The best you can hope for is the cops to have them move so they are not disruptive to you. Have you tried asking them to move your self? From a safe distance of course.