I think it's actually a disadvantage in some ways to be transferring from violin: someone who starts on the viola and reading alto clef doesn't have to get over associating the note in one particular space or on a line with a certain fingering which is different on the alto to what it is on treble - ie I actually have to think momentarily when I see a C below the stave on the alto clef, because in my head it's irrevocably B, 2nd finger on a G string - to play it as an open string will probably always feel slightly weird as I played the violin as my first instrument and the notes and relations and associations on it will probably always be more natural to me than those for viola. Someone who's starting from scratch has no such preconceived assumptions to get over.
It's a bit like learning languages, people always think, when I tell them I did Russian at uni, that "oooh the alphabet must be so hard", whereas actually because it's mostly SO different, it's not really a problem, whereas I think sometimes languages that use the Roman alphabet but have very different pronounciations of certain letters necessitate more mental agility especially on first learning them.
I find I can know what the notes are, ie say "that's a C, that's a D" etc, and have a bash on the piano or some other instrument where the notes are laid out before you, OR I can play the notes on a viola. Playing what I see on the viola and simultaneously being able to say or think "that's F#, that's an A" etc does my head in