My son has autism so this is a familiar topic to me.
We had annual passes to Universal 2 years ago and have not gone since, but I think their policy would probably be the same-
After you get through the admissions gate go directly to the customer service office. When you ask for a disability pass they will tell you that all attractions are accessable and passes are no longer given out (this became the routine when too many people just rented a wheelchair for their otherwise-healthy grampa and then claimed they needed a pass for the family)- but you must tell them your child has autism and in most cases no further explanation is necessary, the pass is issued.
By law (ADA) they cannot ask you for any note or proof of disability, but if you don't mind obtaining and carrying the paperwork, I guess it could not hurt. I have never found it necessary. (After letting my son spend 5 minutes in the office it is pretty clear he is"different". I only had to explain the disability in any detail to a few employees, the rest seem to have been briefed on the benefits to everyone of keeping an autistic child from getting overstimulated)
The main annoyance I had with the passes was that they made me get a new pass each and every time I came to the park, even though we had annual passes for IOA and USF. There were many days the customer service office would be very crowded and hot and just getting the pass could take a half hour and cause my son to act out. One smart thing I did was have them put a notation their computer so they could just look up his name and see that we should get the pass without a hassle.
Busch Gardens has a much better policy- when I get our annual passes there they give me a laminated disability card that expires when our passes do. This was a big reason that we have been going there the past 2 years!
Hope this helps- Good luck!
