I have been in many a southern restaurant and prayed grace, using the sign of the cross before and after, and had waitresses come up to the table and thank us. Their response is generally…"I was happy to see you making the sign of the corss…it seems few people even bother to say grace anymore. It’s refreshing to see that some people still thank God for the food that they eat. "
My sister worked in a place where many of her co-workers swore like sailors constantly.
She said she began to very subtly, and with very small motions, silently make the sign of the cross when a particularly bad cuss word was uttered. Rather than draw ire, it caused people to be aware of just how OFTEN they cursed, and they cleaned up their act substantially.
So it can have positive effects.
I’m never worried/shy to cross myself in public. It’s part of who I am. If it’s a problem for others, well, then it’s just their problem.

I often cross myself in the car when an ambulance speeds by and say a prayer for whomever is in need, as well as those first responders.

*(I can’t believe no one has posted this smiley yet, LOL) *