Is he crate trained at home? Have you done any obedience with him? If he is crate trained, bring it with you. If he's not, put him into a down/stay when someone comes, have some YUMMY treats (if he ignores the treats and wants the person, then the treat isn't yummy enough). Ask for his attention and allow someone else to answer the door. The only person who pays attention to the dog, who even talks to the dog, is the person holding the treats.
Sometimes when young dogs get exhuberant greetings from "company", they start to get overexcited when someone arrives, making greeting company difficult. Teaching the dog another behavior can be very helpful, or in a homecare situation, crating the dog might be best and leave training at home.