Though Julieta Venegas doesn’t officially clock in as UNICEF goodwill ambassador till Sept. 30, the Tijuana-born singer-songwriter is already looking into the plight of impoverished children in her country. She was in Chiapas last week visiting the frontier area of Tapachula, which is known as a crossing point for undocumented migrants going northward and as a center for the sex trafficking of women and children. The 38-year-old tweeted about the experience, describing it as “muy fuerte.” Venegas is the second Mexican to join UNICEF in this effort. The other is actor and singer César Costa, who received the designation in 2004. Good luck, Julieta!