Hi RJ,
You make a very good point about the quality of training. There are literally more wannabes than there are good trainers, and the quality of the training definitely has an impact on whether your chosen course of action will work.
However, on the issue of what you will do, the thoroughness of the training is the sole determining factor. If the training (good or bad) was thorough, then you will act in accordance with it.
As for the specific hypothetical you proposed, I'm not going to fault the decision to or not to get involved. You definitely don't want to start a gunfight if there is no shooting yet, and you don't want to create additional danger if you believe based on your observations that they are just going to take the money and leave. However, if you believe that shooting is likely, why not shoot one - or hopefully both - robbers before they know you are there? Let the first person to be suprised by getting hit be one of them and not one of the innocent bystanders. Wait, and it might be too late to safe someone.