Rubuta ci gaba don wannan sakin layi - Villalobos na ɗaya daga cikin manyan shugabannin Sojojin Juyin Juya Halin Jama'a, ko "Ejército Revolucionario del Pueblo", ƙungiyar da ta bayyana a El Salvador a farkon shekarun 1970 a matsayin ƙungiya mai sassaucin ra'ayi na ƙwayoyin cuta tare da tushen a cikin ƙungiyoyin Marxist da na hagu na Katolika. ERP na ɗaya daga cikin ƙungiyoyi biyar da suka haɗu a 1980 don kafa Farabundo Martí National Liberation Front a lokacin Yaƙin Salvadoran.
, wanda 'yan banga na hagu suka yi yaƙi da gwamnatin hannun dama ta El Salvador da sojoji suka mamaye kuma Amurka ta goyi bayan ta. Dalibin ilimin tattalin arziki da kuma 'yan gwagwarmayar hagu, Villalobos ya shiga ERP a 1971, yana da shekaru 19. Tun daga wannan lokacin aka zarge shi da hannu a cikin kisan da aka yi a 1975 na Roque Dalton, mawaƙin juyin juya hali kuma ɗan'uwan shugaban ERP wanda abokan aikinsa suka harbe shi bayan gwagwarmayar iko a cikin ƙungiyar ta haifar da zargin cewa shi ɗan leƙen asirin CIA ne. A lokacin, kisan ya haifar da rarrabuwa da zargi a cikin ERP da suka daga wasu 'yan hagu, amma bayan 1980 Villalobos ya tashi ya zama ɗaya daga cikin manyan masu dabarun yaƙi na FMLN. An bayyana ERP a karkashin jagorancinsa a matsayin "ƙungiyar soja mafi inganci a gefen hagu na Salvadoran" a lokacin yakin basasa, tare da Villalobos yana haɓaka "sanannun ƙwarewar dabarun ƙwarewa". Jaridar Financial Times ta kwatanta Villalobos a matsayin "Maigidan gaske na yaƙin guerrilla na Latin Amurka na ƙarni na 20", sama da Che Guevara.