There's a really good book that will give you a great overview of diabetes management. It's by Riva Greenberg and is called "50 Diabetes Myths That Can Ruin Your Life; And the 50 Diabetes Truths That Can Save It."
Insulin's job is to transport the carbohydrates we eat into our cells to give them energy. From a blood sugar perspecitive, your body doesn't care if the carbs come from a plain baked potato or from a brownie.
Type 2 diabetes means the body is making lots of insulin but is not sensitive to it. So most type 2 diabetics try to limit the number of carbs they eat. Ideally a low carb diet (meals of 30g of carb or less and snacks of 15g of carb or less) require little insulin and help blood sugars regulate. It can be hard to eat low carb, but any improvements will help.
Diabetes educators and nutritionist recommend non-starchy vegetables because they're healthy and they tend to have few carbohydrates. But you have to find the foods that work for your fiance and his lifestyle.
Some of the worst offenders for me are fast food, potatoes, regular soda, juice, cereal (except Cheerios or oatmeal), pasta (except for the high protein kind), pancakes with syrup. Low carb foods don't raise my blood sugar at all, like eggs, meat, cheese, beef jerky, sugar free jello.
The best thing to do is to come up with some possible meal options. Fajitas with 2 small corn tortillas (or low carb tortillas) might be a good choice. Have your fiance test his blood sugar before eating and then 2 hours after eating. That post meal number should be back in a good range. If it's not, then you may need to cut the carbs in the meal. There's another great book you can get for $8 at WalMart or any bookstore called "The Calorie King Guide to Fat, Calories & Carbohydrates" that will help you look up carb amounts. You can also use smartphone apps like the Calorie King one or Lose It! to get carb amounts.
Exercise makes a body more sensitive to insulin, so that's why doctors recommend a person with diabetes be active. If your fiance can exercise a lot, he can eat more carbs and still have decent blood sugars.
Hope that helps.