GENERAL: I don't have authority from the Mexican Government's Secretaría de Comunicaciones y Transportes (SCT) yet. Can I still make application for OP-1(MX) or OP-2 authority?

Yes, you may apply without the SCT authority.  However, you wil lneed to have the SCT authority (an RFC number) before FMCSA will issue the OP-1(MX) authority or OP-2 certificate of registration.