What indicates that bilbo is fond of visitors

There is a clear indication, after Balin arrives, when the narrator states of Bilbo that "He liked visitors."
When Bilbo first encounters Gandalf, he invites him to sit down and smoke a pipe. Since Gandalf is a rather un-hobbitlike stranger, this also indicates that Bilbo is hospitable and likes visitors. Once Gandalf identifies himself, Bilbo invites him for tea, again suggesting that he is sociable and enjoys company. His hobbit hole is described as having multiple pantries which suggests that he is prepared to entertain guests.
When Bilbo first encounters Dwalin, another stranger, he invites him to tea. As the dwarves keep arriving, Bilbo is hospitable and offers them food rather than telling them to leave. He has a wide range of food to suit all possible guests and brings out just what each guest wishes, suggesting that he is a well-prepared and experienced host.