From my experience, dining with others is more a social gathering with the meal being secondary. If I personally had an inability to follow conversation in a group of friends and acquaintances, I'd more than likely graciously decline the eating of a meal with them simply because I wouldn't be able to participate in the main reason people gather together to eat. That's just me though and I'm in no way saying Frank should follow what I'd do.
Usually you will not be informed in advance that the exact nature of the conversation at that time will be terminally dull or incomprehensible. You may desire the company, but the company may not make the point of ensuring your enjoyment of the conversation.