There is a wonderful resource at http://www.eeoc.gov/policy/docs/accommodation.html regarding ADA and what reasonable accommodation is. It is an easy read and very informative. Generally, ADA doesn't apply to small employers and you do not state how many employees work at the restaurant. However, I would urge you to speak to an employment / employee rights attorney and have them assess your case.
Washington's Law Against Discrimination could apply. You should file a complaint with the Washington State Human Rights Commission, and consult with an attorney experienced in filing claims under WLAD,
I have filed a similar case within the last month and have settled other cases under that law.
You do need to specifically request reasonable accommodation, usually in writing.