Hated clarinet.  Could not figure out how to get any sound out of it.  I'm too petite for the bass.  I have big hands, though, so I suspect I won't have trouble with the viola. 
I was always fantastic at sight reading.  My piano teacher used to laugh at me because I would sight read through what I didn't want to practice, and she could tell, but it was still good because I sight read well.  Still do.  Worked out well for being in chorus. And orchestra.  When I was in middle school, we had an audition-only orchestra. I was the only person in it who was not taking private lessons, and I was a first violin my second year.  Credit it to sight reading.  Just learning the new clef will be a challenge.