Are there any limitations on the ADA's auxiliary aids requirements?

Yes. The ADA does not require the provision of any auxiliary aid that would result in an undue burden or in a fundamental alteration in the nature of the goods or services provided by a public accommodation. However, the public accommodation is not relieved from the duty to furnish an alternative auxiliary aid, if available, that would not result in a fundamental alteration or undue burden. Both of these limitations are derived from existing regulations and case law under section 504 of the Rehabilitation Act and are to be determined on a case-by-case basis.