In the United States, both pronunciations are common. The "roo" form tends to be heard when people are trying to be careful about pronunciation, in formal situations. I started to write my own explanation, but the usage note in the "American Heritage Dictionary" is perfect so I'll just quote what they say:
"The preferred pronunciation among usage writers is [the "roo" form], but in actual usage [the "yoo" form] is far more common and so cannot be considered incorrect. The loss of the first r in this pronunciation can be accounted for by the phonological process known as dissimilation, whereby one of two similar or identical sounds in a word is changed or dropped so that a repetition of that sound is avoided. In the case of February, the loss of the first r was also helped along by the influence of January, which has only one r."
As a child I certainly started out saying "Feb-yoo-wary" because I thought it ought to follow the same pattern as "January," and needed to be corrected.
A similar situation exists with the word "library." In the US, most children, and some adults, pronounce it as "lie-berry." In this case, though, American Heritage does not include this pronunciation, while Merriam-Webster calls it "nonstandard."