Do you let people know that you have been deployed?

I used to tell people. Not anymore.
First my reactions from civilians have been blase to terrible. I was never asked questions that I felt were intelligent. Being asked if you have killed people or whatever is insulting. I have had people try to lecture me for various conspiracy theories they ascribed to. Too many negative things to write when thinking about times I have tried to interject my service into a boring conversation.

However I do have a couple lifelong friends who many times out of nowhere tell people "Hey my best friend here was in the Iraq and Afghanistan wars" Now the normal response people give him is to ask "really" (and that response is "Yup.") or, "how was it" (and that response is "hot")

Sadly too many who try to be supportive talk about how they hate Muslims (I do not) or how we should just nuke the place (another thing I do not support) So I try to stick to other topics in public.

I share with vets normally; in my particular case after my mobilization, I nearly died of a "MI" while in training. My buddies never held it against me that I was not deployed with them ; they were just glad I was alive.
I knew a man in my unit that died, (after years of suffering from IED burns, from his fuel truck) most civ people only understand the "sensationalism or entertainment of war" -- and although I was not deployed; I am haunted at times by my friends who were, and that I was not with.
Most veterans seem to understand this - but rarely does "an air stealing civilian" just kidding>(lol) ...
So I had to learn the hard way, to shut my mouth about myself, in what I have done, and not done.

Nope, not at all. Only those with a need to know.

My brother thought I was a desk jockey until I told him I left the FOB 4 or 5 times a week.

I only share with people that I know that served in the military, my own wife does not know she has asked once when we were dating but 17 years later she does not ask.

Option 4, it is situationally dependent.

I never hide it, but in some conversations it is just not relevant.

ie...

"Thank you for your order, would you like fries with that?"

"As long as their freedom fries. Who's got two thumbs and deployed? This guy."

And there isn't very much that people NEED to know.