Often I will use plain greek yogurt in the place of cream/half & half in recipes to make a cream sauce. The 0% kind doesn't work so well, but 2% is fine. You usually can use less than you would if you were doing cream (because it's less liquidy), so I wouldn't use 2 cups of it... just add it til your sauce is how you want it. Also make sure what you're adding it to isn't too hot, and that you've taken it off the heat when you add it. I tried adding it once to a very hot curry that was still simmering and it curdled, but I've done it successfully when adding to red sauces I had taken off the heat.