Will others be able to tell if I'm on dialysis?

Most time not. Dialysis will take at least 3 h 3 times a week from your time and if you have a catheter for dialysis that is obvious that will be very hard to explain to others. Symptom wise some patients may feel drained after hemodialysis and they may have anemia but these symptoms are not specific for dialysis . In conclusion if you do not have symptoms it is very hard to tell.
Probably not. No one can tell you are on dialysis just by looking at you. If they are familiar with dialysis however, they can tell if they can see your access, graft or fistula. If your access is in your arm, make sure you wear something to cover it up if you don't want others to see it.