I've got good news and bad news:
in 2001 we were staying at the Hard Rock Hotel, and had just embarked on our first day in IOA. We were having lunch at Mythos. Our DS (then age 13) has life-threatening allergies to milk, eggs, nuts, and treenuts. This was known both to the manager and the server, in particular because his burger had a yellow tomato, which in the dim light looked like cheese, and the manager had rushed over to check it. For dessert DS ordered a peach cobbler, which the server said 3 separate times was nut free. DS took 2 bites and asked if she were sure. She said yes, DS ate 2 more bites, and went into anaphylaxis symptoms. I sent the server to check, and she never came back. I went running into the kitchen, and screamed at them to check and see if there were nuts in the cobbler, a chef immediately said there were ground pecans in the topping. By this time DS was throwing up in the men's bathroom, which I invaded with the epi-pen, while yelling to to the manager to call an ambulance. (Really surprised the guy at the urinal). First aid arrived within 2 minutes with a wheeled stretcher. They took us to first aid, administered another epi, then sent us by EMT van to Centracare, which started a steroid drip, and sent us on to Sand Lake hospital.
I was given the contact info for Risk Management; the first aid people knew where we were staying, and I was most surprised not to have heard from them. When we finally got home that night, very tired and depressed--and with DS in a wheelchair due to the complications from the meds (long story)--we were about as low as you could feel. I sent Universal Risk Management a long email report of the episode, expressing our frustration and sense of outrage at not hearing from them.
We said we didn't want to see anyone fired, but certainly hoped they would address training issues for food allergy response, and that this incident was intolerable at a fast-food establishment, much less a restaurant which aspires to 4 stars.
The following day, determined not to have our trip ruined, we rented a wheelchair, and were doing US. Up panted a "suit"--a wonderful man in charge of Risk Management of Universal Florida. He found us by walking around the park looking at the backs of wheelchairs, since my cellphone wasn't ringing through. He escorted us to his office, put us on the phone with the head office in New York, and we ended up being comped for our 4 day stay, with VIP tours in both parks, and both kids being authorized to spend whatever they wanted anywhere on Universal property. (Still much cheaper than the lawsuit we decided not to file.) We had a $300+ dinner at the Palm on the house (no problems with nutfree there)
But, DS was still in a wheelchair for the entire trip, and it was the beginning of several nightmare months of gastro related problems caused by the reaction.
We went back in 2003, and ate at all the same places without incident. It seemed to me that there was more attentiveness to food allergy concerns--I know for certain that our episode when they nearly lost a guest through their own fault shook them up, and we saw an immediate change in how they responded in US restaurants when they noted the allergy on the ressie on the following days.
DS did NOT order any desserts or any baked items which might have hidden ingredients. If all you're dealing with is a nut allergy (not that it's "all", but it's not as complex to manage as milk/eggs), then you should be fine and very fine if you stick with simple foods like burgers, fries, chicken strips, etc.
I wouldn't hesitate to eat there, but question carefully. And, it goes without saying, don't ever leave the epi-pens behind. If we hadn't had ours, our DS would not now be 17, giving us a run for our lives. (Why can't beer have nuts?)
