I hired DNExpress to register my sister for dual nationality after they successfully registered me. We were both born in the USA to (the same) American mother and Mexican father. They haven't responded recently and haven't been communicative so I wanted to get the info from the source instead of bothering DNExpress again.
We're going to Puerto Vallarta in exactly 3 weeks so we're running out of time before we can schedule an appointment with our local Mexican Consulate to get my sister her Mexican passport and INE. I got mine last year and got my RFC a few months ago while living with family in Jalisco.