My understanding is that the public liturgy of the Church is the Novus Ordo in the vernacular, in accord with the documents issued by Pope Paul VI making it mandatory. The faithful have a right to the lawful Mass. If there are several Masses being offered on a given Sunday and if the parish is large enough to be blessed with more than one priest, diocesan permission may be given for one of them to be in latin, but it has to be specified in the parish bulletin ahead of time, and there must be sufficient parishioners who make this request to the Bishop.
In my area, the parishes are rural and one priest must celebrate the vigil mass and the Sunday liturgy in his home church, in addition to a mass in the mission church which he serves. There would be no possibility of doing the main Sunday liturgy in either church in latin in this case.
My pastor had a request from one lady who wanted the Tridentine rite celebrated in our parish, but she had no other supporters who wanted it, so the Bishop did not grant permission.