As a prank, I sometimes go into a Mexican restaurants and yell ICE.
That's awful. Why would you yell ICE?
I'm going for my favorite dish - the ice cream - and I have a certain way of indicating my order - yell ICE.
Pranks can be fun if everybody likes them. Joking about ICE in a mexican restaurant will be seen as racist and people will think that you are a bigot.
I'm white, but I'm not racist.
Whether you accept it or not, your joke is racist and it's hurtful and harmful towards others. You should reconsider your actions and refrain from doing it again in the future. Have you thought about how this makes people in the restaurant feel?