Complex sentence: On December 5, they were notified that Andrés Caso Lombardo, Secretary of the SCT (Ministry of Communications and Transportation) would not be meeting with the San Diego delegation and instead would be meeting with Mexico's Under-Secretary of the SCT Gustavo Patiño Guerrero.
Split into simpler sentences: On December 5, they were notified that Andrés Caso Lombardo, Secretary of the SCT (Ministry of Communications and Transportation) would not be meeting with the San Diego delegation. The San Diego delegation was met by Mexico's Under-Secretary of the SCT Gustavo Patiño Guerrero.