Can you pray to St Valentine?

Answer 1

Of course you can pray to St. Valentine, of which there were a number of martyrs in the early Church of that name. The St. Valentine who is commemorated on February 14 was a priest of the early Church and martyred about the year A.D. 270. The greatest part of his relics are now in the church of St. Praxedes. From the Saints and Angels website:

The origin of St. Valentine, and how many St. Valentines there were, remains a mystery. One opinion is that he was a Roman martyred for refusing to give up his Christian faith. Other historians hold that St. Valentine was a temple priest jailed for defiance during the reign of Claudius. Whoever he was, Valentine really existed because archaeologists have unearthed a Roman catacomb and an ancient church dedicated to Saint Valentine. In 496 AD Pope Gelasius marked February 14th as a celebration in honor of his martyrdom.

Answer 2

Yes. Saint Valentine is recognised by the Catholic Church. However, there are good grounds for believing that the man behind the St. Valentine myths never really existed. The existence of purported relics is, of course, not evidence that the saint really existed.