Not at all a bad topic; and one that we've discussed at length without any real definitive solution. It's hard to say whether or not you should tell someone on your first date that you carry a weapon. But at the same time, if it's part of who you are, don't they deserve to know before you get involved? I think the having the mindset and decision to carry a weapon everyday is tantamount to a social philosophy, and one that is as personally indentifying as what religion you subscribe to. So I ask you back, when is the preferable time to discuss what religion you are with someone you're dating? It's all about who you are and how things go.
I told my wife before our first date what I believed and what I carried. She grew up in a gunless household where "No one would EVER NEED a weapon," so she really didn’t' know what to think about it; she just knew she didn't like it. But I sure got that first date, and a second, and so on because she understood that I COMPLETELY understood my personal decision. Now she wouldn't be totally comfortable in a household where there wasn't a gun, or five.
It's all personal preference, and how prevalent the topic of carrying a weapon and self defense is in your personality. If it's a big part of who you are, then it'd be better to discuss it sooner rather than later. The important thing, however, is to be tactful about it; along the lines of, "I'm really opinionated about politics, and I'm curious to know what you think about some things. What are your thoughts on, say, gun-control?"
This would be much better than the alternative option of, "Hey, I'm mostly a stranger to you and I'm carrying a loaded gun. Would you be so kind as to trust me enough to get into my vehicle and let me take you to a place of my choosing?"
Just be mindful and courteous. And read up and be prepared to answer a few questions. The more knowledgeable and politely confident you seem, the more accepting other people that are on the fence tend to be of our viewpoints.
~LT