I would say talk about it after you're seriously dating someone. It's not the sort of thing you would want to disclose on a first date, because that would be sort of weird and maybe give your date the wrong impression (like that you're sure you're going to get married because of this one date). On the other hand, though, I would say if you're engaged to someone they should already know about your infertility. Somewhere in between that first date and getting engaged, you should talk about it. I'm not going to give you a certain number of dates or weeks after which you should have talked about it with someone, just play it by ear and mention it after you're already in a serious relationship. Nobody else really has any right to know, anyway.
You say you don't want to "waste anyone's time," but I would like to push back on that idea a little bit. First of all, dating someone who you don't end up marrying isn't necessarily a waste of time. If both of you know that it could absolutely never work out and you aren't attracted to each other at all, sure, maybe it's a waste of time. But other than that, dating isn't a waste just because it doesn't lead to marriage. It's fun, it hopefully opens up your worldview a little by getting to know someone else's, it teaches you about what you value in a relationship, it helps you develop good attributes, it teaches compromise and communication skills, it gives you an idea of what dealbreakers you have, etc. Don't feel like you're wasting someone's time any time you go on a date with someone and it doesn't work out, or even (especially) any time you're in a serious relationship and it doesn't work out. If you don't get married, at the very least you get to know someone else, and you get life experience, and that's valuable and worthwhile.
Furthermore, I don't think that you being infertile would be quite as much of a dealbreaker as you think. Once most people are in a serious relationship with someone, they come to love each other for who they are, regardless of if their life together would end up exactly like the fairy tale life they had planned before meeting and falling in love. Hopefully you're (and this is the general "you" here, applicable to everyone) able to build a strong relationship with someone regardless of how many kids you do or don't end up having; the children shouldn't make or break the relationship. Also, infertility is much more common than people seem to think. Most people probably find out they're infertile after they start trying to have kids and can't, but it's not like their marriage is somehow suddenly invalid, or that they tricked their spouse into entering a childless union. I'm not trying to downplay the pain of infertility at all, but if a couple has a healthy, strong relationship, they should be able to get through it together. You happen to know right now that you're infertile, but there's no guarantee that a girl who breaks up with you because she wants to have kids would be able to have kids with some other guy (maybe in this hypothetical situation she's infertile, or maybe he is, and they just didn't know about it). There's no reason why you would deserve less happiness and love in your life than anyone who finds out they're infertile after marriage (or someone who's completely fertile. Everyone deserves love and happiness regardless).
Good on you for making peace with your life. I wish you the absolute best of luck in the dating scene.