They are Very careful about cross contamination. Just let them know before they start your order that you have a severe gluten allergy and they will literally drop everything, switch out every spoon for the items you're requesting and bag it separately. Make sure to get the gluten free corn tortillas. There's still a small chance of cross contamination, but it's way smaller than you would find at most other restaurants. The single serve chips & salsa/guacamole aren't prepared as carefully, so proceed with caution on those. They have an easy allergen menu chart online to help you know which foods are have gluten already and which don't.
— Somewhat
— Gluten-free items are marked on the main menu
— Some
— Excellent