[ytse43]

(Apologies in advance for the what follows. Blame/Thank the whiskey.)

Yes, I can read grand staff (G treble clef, F bass clef) notation. I have no experience with the C alto clef.
I was in symphonic band from 6th grade on, starting with the alto saxophone, then switching to the tenor. In hindsight, I probably should have stuck with the alto; tenor parts were boring--Jazz band made up for that! For marching band, I played the tenor sax, euphonium and tuba, and did a bit of drum line. I also played electric bass for school musicals. In addition, I was in choir and Madrigals (Renaissance music, sung a cappella), and sang both bass and tenor.
I studied classical piano for ~10 years (but started "late", so never got "great"!) I still play, but don't have a keyboard at home. (Need to remedy this)

I am self-taught on guitar, but had the benefit of (see above). I learned to read standard notation for classical guitar, but also TAB for all genres.

As to sight reading, at the height of my sax playing (haven't played since high school, nor have a sax to play), I could sight read pretty well. I was never great at sight reading for piano--likely due to looking down at the keys too and not getting corrected of that habit. On guitar, I am decent, and hopefully getting better.

Sight reading is a skill, and skills can be improved upon. If one plays an instrument, but doesn't read notation, then one is likely learning by ear, which is a skill, and as such, can be improved upon. I include this, as I not great at it--partly because I read?

All this said, learning to read music is certainly easier achieved when younger, as is the case with most skills, languages especially, yeah? Is it worth it? I can see no demerits.