Federal and state laws give persons with disabilities the right to not to be discriminated against in the areas of employment and housing -- and these rights include being able to bring a service dog into public areas and rental units.
A disabled person seeking a rental should not face questions by landlords as to whether they have a disability or illness, nor a request to see medical records. After moving in, the landlord may have to provide accommodations, at the landlord's expense, and may have to allow the tenant to make reasonable modifications to the living unit, though not pay for it.
Successful travel depends on knowing one's abilities and needs for modification, the disability rights laws that apply to the settings to be visited, and who to contact if any problems arise during travel.
Federal laws, including the Americans with Disabilities Act, prohibit health care providers from discriminating against people on the basis of disability. If you are blind or have low vision, this means that, among other things, you have a right to receive health care information in “alternative formats” that you can read.