I have
ॐ on my left deltoid, which is visible only when I wear a sleeveless t shirt or am shirtless (beach, etc.). Few people notice it or even know what it is; they probably think it's a Chinese character that is oh-so-fashionable to have.
However, one young guy at the gym saw it and said "why you have that?" I don't know if he was Hindu, or even Indian, but he looked south Asian. I said "well, uh... because I am Hindu". He said "why?" I said "because it's right for me". He had a sort of mocking grin on his face. Ahimsa notwithstanding, I'd have bench pressed him had he given me grief.
Another time a young Indian cashier at the supermarket saw my pendant. It is not unlike my avi, but it is not those colors. Rather is it is copper and silver, with a black inscription on a gold chain. She said "oh that is so beautiful! are you... ?" and stopped short. I smiled and said yes, and we chatted. She said she knows so little about it (the faith).
If someone sees my neck beads or pendant (I tend to be decorated like a Krishtmas tree) peeking out of my shirt, all well and good. They usually don't know what they are anyway, especially white people. Only occasionally I'll wear my pendant outside a pullover shirt only because... well, it's pretty.