Is Mary omniscient? omnipresent?
She is with Christ, Who is.
I'm not sure how annalex will answer for the Latins, but for the Orthodox, as the Theotokos and Ever-Virgin Mary is most assuredly among those who are saved in Christ, and as salvation is understood by the Orthodox as theosis--participation in the Uncreated Energies and Life of the All-Holy Trinity--I see nothing absurd in understanding her to participate in God's omniscience and omnipresence.
For myself, I will not presume to suggest that participation is so full so that she herself might be termed omniscient and omnipresent, but I am certain she participates in those qualities in measure sufficient to interceed for all the faithful who have inherited Christ's words to St. John, "behold your mother," and call upon her prayers as we would the prayers of our natural mother.