No, the US has no official language, but English is the de facto national language. Some laws require official documents (election forms, immigration forms, etc.) in multiple languages. You often see signs including other languages in specific locations depending on the local population (Spanish in the Southwest and Puerto Rico, French near French Canada, Native American near reservations). In addition, some state laws require the use of languages important to their local populations (e.g. Spanish on legal and warning signs in areas with a lot of Spanish-speaking citizens)

This particular law is a state law passed in Texas. It requires that schools post any privately donated signs with this message. The law is written in English, so the case is not a slam dunk. A court could find that the law specifies the phrase in English and only applies to signs with the English phrase.

This Texas law is an example of the recent trend in the state's politics to leverage private actors to enact policies that may be constitutionally questionable. They also did it with their recent abortion laws, that enable private individual and organizations to sue abortion seekers and providers for facilitating abortions, even if the people bringing suit have no relationship to the abortion activities. The constitutionality of such laws have not been determined in court yet, so they may yet run into issues.