Over my years as a blogger, I have been repeatedly asked to my opinion on the apparitions at Garbandal. This is no doubt because of my writings on other questionable apparitions, such as Medjugorje and Bayside.
Garabandal is a quandary for many traditional minded Catholics. It lacks some of the excesses of Medjugorje (forty thousands plus messages, the charismatic stuff) as well as the absurdities of Bayside (T.V. being an invention of the devil, Pope Paul VI being replaced by an "impostor", etc.). In addition, it promotes traditional morality, calls us to penance, promotes Eucharistic devotion, and its timing from 1961 to 1965 coupled with warnings of an imminent chastisement are very convenient to Catholics who see Vatican II as a fundamental rupture with Tradition. Its condemnation of the contemporary generation of bishops - the Conciliar generation - also plays into the hands of Traditionalists.
It is not my intention to enter into a point-by-point critique of Garabandal, but rather to state my personal opinion on the matter. I do not believe the apparitions at Garabandal are legitimate, nor have I ever thought otherwise. Since I am not offering a refutation but merely stating my thoughts, it suffices to say that my gut has always turned me away from this apparition. Something about it does not seem right. I actually suspect the demonic may be involved. Mary's alleged request to not bring any blessed rosaries before her because she wanted to bless them herself has always given me caution.
There are other reason as well. But, as always, the biggest evidence against their supernatural character is the continued stand by four successive bishops of Santander against the legitimacy of the apparitions (see here). The seers all at one time or another denied the apparitions upon interrogation, and one, Maria Cruz, continues to do so to this day. Some quotes from Maria Cruz from 1984:
"I've never seen the Virgin at the Pines or any celestial being...[Conchita] suddenly went into ecstasy; that sort of comedy scared us and we thought it would end badly. She put into the heads of the three of us that she had seen the angel." [...] (source Spanish; source English)
In 1992 Maria Cruz further reflected on the pressure the seers were under::
"The people tormented us so that we see the angel and the Virgin, and these fanatics came to write a message, as always happened in other apparitions, like Lourdes or Fatima. [...] Every time I have the occasion, although I don’t look for it, I say it, but they don’t want to hear this truth." I remember perfectly how Conchita, who always used to organize jokes, invented everything. She did it without bad intentions, but the situation became so complicated that we had to go on. [...] Do you believe that the Virgin Mary would do such stupid things? [...] But I'm afraid to be in the papers, because then they make life impossible for my other, who still lives in the village, and it is full of fanatics." [Gabriel Carrión López, El lado oscuro de María, Aguaclara, Alicante, 1992, pp. 106-107])
One last thing: According to Garabandal, the Blessed Virgin Mary has promised that she will one day restore the sight of the blind man Joey Lomangino. This is to happen on the same day as the promised "Great Miracle." Joey Lomangino is now 86 years old. If this man dies without having his sight restored to him, then this is absolute evidence of the falsity of these apparitions. The Garbandal people will probably try to wriggle out of it - say that the promise was of spiritual, not physical sight, or perhaps say that he recovered his sight secretly hours before death or something like that. But if we see that sort of mental legerdemain, it will be a pretty clear sign about Garabandal, though perhaps not the sort its enthusiasts were hoping for.
For these reasons, and many more I will not go into here, I do not believe in the authenticity of the Garabandal apparitions nor do I endorse them in any way.