The two most significant people Benito meet at the party of Posey Pendergast are Dolores and Herman Tolliver. Dolores is a former girlfriend of Benito, and we are told that Dolores actually prefers women to men, and Benito remembers that she told him she was in love with Posey Pendergast, the host of the party. He reminisces about the way in which Dolores tried to encourage him to pay after they had intercourse, as it would be more exciting. Benito remembers refusing this suggestion.
Secondly, Herman Tolliver is a lawyer who joined with Benito many years ago to buy up old hotels. Benito was a sleeping partner in this business, and deliberately did not inquire too closely into the precise nature of how it worked, as he knew that the money he received from it was a result of using these old hotels as brothels. The significance of this time in his life is shown by the way that Herman first met Benito when he met Elizabeth. The flashbacks that Benito experiences indicate that he felt the need to gain more money so that he could gain Elizabeth. Now, in the present, meeting Herman makes Benito ashamed, but he allays his guilt by reflecting that he used his profit from this illegal business to fund free clinics to support those who were not able to access medical care because of their poverty.
The people that Benito meets at this party are therefore important because of their significance to the main protagonist and his past.