If we're talking for extended text, I'd say something like Caslon or Janson. For what purpose exactly is this intended? Knowing that might suggest other, or more appropriate, choices.

Depends on whos speaking too? If it's a short play about two housewives gossiping in the kitchen..vs two men sitting at a table...

Well, that's hard to say. I'm building a tool for two people to use when having an extended, informal conversation. It's a replacement for long conversations that might otherwise be held through email. So the two participants and what they say may vary widely.