Green’s Dictionary of Slang

(drugs) opium from Veracruz, Mexico.

1955		H. Braddy ‘Narcotic Argot Along the Mexican Border’ in AS XXX:2 87: CRUZ (Sp.), n. Opium.
1957		El Paso Herald (TX) 3 Oct. 17/5: A few examples of [...] ‘calo’ [...] cruz — opium.
2001		ONDCP Street Terms 7: Cruz (Spanish) — Opium from Veracruz, Mexico.