shawn

Quiet? Not usually. Most gliders have noticeable wind noise.
Turbulence? Depends on the weather, but *usually* is a fair comment.
Not necessarily bang-your-head-on-the-canopy turbulence, but some bumps
and vibrations are typical. The weather that creates unpleasant jet
travel is the stuff of great soaring days. Cold-depends. Where (Rio?
Fairbanks?), what season, how high? For an intro ride, whatever clothes
you're comfortable in on the ground will be fine.
If you're flying in a country that regulates glider flying, the glider
will be safe. How well do you know the pilot or their reputation?
That's where the risk would be. Are they an experienced instructor who
flies four days a week or someone who got their check ride two years ago
and has flown three times since (Yikes!). Its OK to ask BTW.
Your first experience will be different from everyone else's, so
detailed descriptions aren't much help. Just go enjoy it.

Shawn