Critics of Arizona’s controversial immigration law are on alert. This week, a federal judge gave the state the go-ahead to enforce the “show me your papers” provision of the law. Now some undocumented immigrants are being taught how to respond. As night falls on a Mesa, Arizona park, worried families, many of them undocumented immigrants, are instructed on what to say if questioned by police. Instructor: “You want a lawyer?” Woman: “Yes.” Civil rights groups are also teaching people how to use cell phones to record video if stopped by the police. The training session was a response to Arizona’s law that took effect this week. It allows police to investigate the immigration status of anyone they stop, giving rise to fears of racial profiling. Defenders of the law say police will not use race when deciding whom to question about immigration status.