I was watching the news and saw an entire family of young kids on a road trip dying from food poisoning after they had stopped to grab lunch at a small diner. Could they have known this would happen within the first few bites?
While our senses can warn us of some potential problems, there are many pathogens that we can't detect by smelling, tasting, or feeling. So, no, you generally can't tell from a bite or two of food. Alternately, if you know how an establishment stores, processes, and prepares the food you are about to consume, you could probably make some meaningful assumptions about the safety of the food your are going to eat. You are always taking a risk when you don't know how food was prepared and handled. The risk may be very small most of the time, but sometimes even the finest restaurants in the world serve food that has been compromised.