McAlisters has an allergy section on their site where you can specify what you are trying to avoid...
Now it does not consider sugar LOL so that would need to be something that was asked about... But at least they can help narrow down the wheat, gluten, soy, milk, peanuts fairly easily... So that way when could get a better idea of what you may want and then talk to them about the sugar.
Keep us posted on how it goes. I am on day 4 and have not eaten out yet, there is a McAlisters near me where I usually meet up with friends once a month, so I am interested to see what they have to say.