JOEL - I don't know what is really going on in the Pentecostal Church when they claim to be speaking in tongues. One can be fairly certain that they are not speaking in the pure Adamic language, because the sounds they make differ from one person to the next. Even though they themselves don't understand what the sounds mean, they believe that they are nevertheless understood by God.
Although there were a few instances of the pure Adamic language(Moses 6:6) being spoken in the early days of the restored Church (See Orson Pratt, Journal of Discourses(JD) 3:99-103; HC 1:297n), I have never heard anyone use it in all my life in the Church. The definition of the gift of speaking in tongues in these latter-days has pretty much been confined to the ability of Church leaders and missionaries to quickly learn to be able to speak in different languages so that the word of God can be preached to all nations. This of course happens on a daily basis.

It is also occaisionally demonstrated at times when someone, speaking in a language different from the audience, is nevertheless understood by the audience through the Holy Ghost. Elder David O. McKay once admonished a predominantly Maori congregation to pray for the gift of interpretation because he could not speak their language. He recorded that many in the audience were blessed with this gift (Cherished Experiences from the Writings of David O. McKay, 53-54).

The Prophet Joseph Smith, like the apostle Paul, said that the gift of tongues is in some ways the least of the spiritual gifts but the one most sought after (see 1 Corinthians 14:8-32; Teachings of the Prophet Joseph Smith(TPJS), 246).
Because Satan is so eager to deceive those who seek excessively for the gift of tongues (TPJS, p. 25, 162, 195), the Prophet declared that anything taught in tongues was not to be received as doctrine (TPJS, p. 229). He explained that "tongues were given for the purpose of preaching among those whose language is not understood; as on the day of Pentecost, etc., and it is not necessary for tongues to be taught to the Church particularly, for any man that has the Holy Ghost, can speak of the things of God in his own tongue as well as to speak in another; for faith comes not by signs, but by hearing the word of God".
For these reasons the pure Adamic language tongue is rarely used today.

I have not heard that the priesthood is required for speaking in the Adamic language tongue. Speaking in tongues is one of the gifts of the spirit (1 Cor. 12: 1-11) that is available to all. The Adamic language was used by Adam and his posterity to the time of the tower of Babel(Moses 6:6) and will apparently be used again during the Millennium.(Zeph. 3:9.)