Deciding when to disclose your disability is your own personal decision. It can be made at any point during the job search process and even after you have begun working.
You can wait until you know what you need on the job before you disclose. In fact it helps if you have thought about some possible solutions to include in that first discussion. This isn't an issue of whether you are being honest or not, it's making sure you first understand the nature of the job so that you can identify and suggest appropriate accommodations. This shows the employer that you want to make sure you are a productive member of the team. Not disclosing at all is also an option, if you do not require any accommodations to perform the essential functions of the job.
After you identify the need for specific accommodations, the negotiation of accommodations is meant to be an on-going, interactive process.
There may be many factors to consider when deciding the timing of disclosure. Here are a just a few:
Disclosing your disability is most effective within the context of presenting your qualifications for a particular position. Use statements about your skills and abilities that include examples of previous successful accommodations and keep the focus of the discussion on the essential functions of the job.
After deciding when to disclose your disability during the job search process, you would then need to do it effectively.
Anticipate and address employer disability-related questions or concerns. Misconceptions about your disability most likely are nothing new to you and the same misconceptions may be influencing the interaction during an interview. Your own level of comfort with your disability and confidence in your qualifications will often put the employer at ease.
Be yourself. Know your strengths and make them known to the employer. A sense of humor, enthusiasm for your major, etc. conveys the most important message -- that you are first and foremost a bright Cal student -- who happens to have a disability.
Prepare and practice your disclosure.