I emailed the restaurant & they replied back within the hour. They wrote:
We can accommodate gluten free. We have corn tortillas available for all of our tacos along with burrito bowls that can all be made gluten free upon request. Please let us know if you have any other questions or concerns. We look forward to seeing you.
Thanks, Calexico UES 1491 2nd Ave New York, NY 10075 P: (347) 967-5955
We will try it out this week and update the information.