This is of course coming from someone rabidly anti- exchange. I ain't eating veggis when I want only garbanzo beans to snack on and I have the calorie's to spare. But I feel like I at least understand the trade offs I'm making.
But that is the key. With Nutrisystem which is pretty much the same plan... just cheaper and not frozen foods. I also don't always follow the exchange rules and will deviate with some whole wheat crackers instead of my protein serving.
But I understand what I'm trading off for as well and what it will do to my plan. Education about nutrition is everything.
As for how to eat off plan, talk to one of their counselors and find out if there is a suggested plan for taking a few days off and eating on your own. I'm not sure how they handle that since they charge you for weeks of use and not just the food. If they have nothing to offer you then I can share with you what the break down is for for my plan in terms of exchanges and calories.