I always announce to the wait staff that I have a Gluten Allergy.

This typically leads down one of two paths: 1) Them apologizing and explaining about shared fryers, cross-contamination, etc. 2) Them asking if it’s Celiac, understanding, and listing how they’ll accommodate me so I don’t get sick.

If those don’t happen then it may be a sign to abort and leave if they don’t know what to say, have to get others, don’t offer to talk to the kitchen staff, etc.