This was the key decision. Mexican food can be yummy, but not so that it makes one forget they don't have lights or not realize it is getting near sunset. Waiting for a different day for Mexican or getting take out would have been a reasonable option or alternately just riding home carefully as they did and then not making it into more than it was on BF. It was a simple and arguably reasonable decision that yummy food then and there was worth the short 3mi ride home in the dark without lights.