What is meant by the United States not establishing a religion is that the government cannot create a religion that everyone in the country is required to follow. It does not mean that the United States is to be free completely of religion. Many of the original settlers in the United States came here for freedom of religion, not freedom from religion. Mentioning God in various public places is exercising freedom of speech and religion, which are very important rights.
No, the establishment clause should not prohibit any mention of God in the public square, The Religious freedom is a fundamental human right that is guaranteed by the First Amendment's Free Exercise and Establishment clauses. It encompasses not only the right to believe (or not to believe), but also the right to express and to manifest religious beliefs.
I do not believe the establishment clause should prohibit any mention of God in the public square. People should be able to mention God, Allah, Buddha; any of them, in the public square. This is the exact type of law this country does not need. These laws are pointless, we shouldn't waste our time setting up all of these nitpicking laws that end up making people miserable.
No, the establishment clause should not prohibit any mention of God in the public square, because people who want to talk about God should have the right to. We have freedom of religion in this country. If a person wants to pray on a courthouse step, they should have the right to.