One of the obstacles of having a PG allergy is dealing with pre-packaged foods. It also gets sprayed on produce, so make sure to scrub all of your produce at home before eating it - even bananas.
It is EVERYWHERE on the shelved, pre-packaged foods and is also in the bakery section of the grocery stores. Make sure to watch out for dessert mixes and salad dressings. Above is a list that Dr. Scheman gave me and it actually gives the exact brands - or some of them anyways! It will definitely train you on the types of things you're going to be avoiding.