I played piano for some years as a child, but never enjoyed it.
I've always wanted to learn to play the violin, and now am realizing that now is as good a time as any.
However, I've been told by a violinist that it is important to at least become proficent on the piano first. Is this true?
Perhaps that is someones idea… not a bad idea…, but is in no way necessary for success on violin or any instrument (other than maybe singing).
****Dedication to your instrument is the key to becoming proficient.
It sounds like you are interested in violin and that is already a good start. Find a reputable teacher for lessons, they are key to helping you "translate" the music from page to instrument as a beginner. Remember to enjoy listening to violin Cd's to hear good models, and remind you why you love the instrument, and what your goals are as a player. Practice time put in will always reward you in future tense.
Best of luck to you and your violin!