I've lived with this new way of life since 2000 and have learned a lot of things . . . some of it the hard way . . by being sick. I've also learned to ask for what I want/need and to keep it really simple or the wait person can get overwhelmed.
If I am driving, I take legal food with me in a portable refrigerator (from Sam's) that plugs into my car cigarette lighter. I bought an electrical adaptor from Radio Shack so I can move it into my room at the hotel. I cook ahead and shop for fresh fruit on the road.
If flying, I take: Home baked muffins and/or cookies, baked or grilled chicken/beef patties, cheese, canned tuna or chicken, veggie sticks, legal trail nut mix, fresh fruit, and bottled water with me; in my suitcase and/or iced in an insulated roller bag that I carry on. When I get to the hotel, I ask for a fridge.
For banquets, I contact the person in charge of food services when I get there, well before the banquet, and tell them I have serious food restrictions and ask if they can bring me non-marinated baked/broiled/grilled chichen or beef or fish and fresh steamed/grilled veggies (whatever they have that is SCD legal); each with butter, salt & pepper ONLY . . . no packaged seasonings, gravy, sauces, or croutons. I usually eat the salad with lemon juice squeezed on top.
When I sit down at the banquet, I tell the wait person serving my table that I have a special plate ordered. If per chance they goof up and I don't feel safe with what they bring, I have my food in the room to fall back on. I've learned to play it very safe and have done fine except once, in New Orleans, back before I learned how to order.
Most hotels can accomodate. Knowing how to order is key to being safe.