Ruby knows Damon and she could introduce Cas and the vampire, but she's fairly certain they wouldn't get along.

Dean is far more complicated than he appears. He also has issues with serious conversations that discuss actual emotions, fears, and hopes, which is part of the reason for the labyrinthical conversations. Dean assumed that Cas only wanted sex when he was human, but this conversation has Dean considering how his bouts of humanity and this place in general is affecting Cas as a whole. Dean's brow furrows and he leans forward, adopting a much more concerned expression and body language. He considers Castiel's words as well as his tone of voice while he takes a sip of his coffee. "Okay. Can we fix it? Do you want to?"