hat is why they speak Russian over there, my Polish neighbor told me, the Ukrainians don't like their own language.
I think it's logical that if you want to move to Ukraine, you should learn to speak Ukrainian in the first place. Russian won't hurt (you can take advantage of the opportunity to learn them both, since they're pretty close) too, particularly in Kiev and in Eastern cities of the Ukraine. Although in the West speaking Russian may bring you into troubles or have you treated not as well as you expected.
Ukrainian if not spoken by everyone is understood by everyone. Go for it and good luck.
P.S. If you are Polish, then studying Ukrainian will be easier for you than studying Russian for it's sort of bridge-language between us two. And I'm Russian.