I've had more men accept than reject and I tend to use the same method (which I have used for my current boyfriend). I don't actually mention it straight away, because it can alter their perception with the negative stereotypes and assumptions they are likely to have. This means as they get to know you, it will be through a "trans" lens, and might make it more difficult to accept. I tend to give it 2 or 3 months to see where it is going - often I have had guys who walked away or just wanted fun, so I saved a lot of hassle in not telling. When it looks as if it's getting more serious I mention it without using "trans" or anything like that - I simply say that I was born with a physical condition where I was a girl but with male organs. (Of course if they say "so does that make you transgender? Then I'd say that yes, that is what you could call it). I emphasise the medical aspect of the condition and also that I have always been female.
The way I see it, there tend to be three types of guys in these situations - those that are amazing and have no problem with it and accept it readily, those that will never accept (perhaps politely, or react worse), and those that are in between, and are not quite sure. Whether you tell early or late will not change the outcome of the first two types, if they are readily accepting, they will always accept, if they won't, they never will, but those in the middle, I find that my approach of waiting a bit can win them round, as they get to know me as ME first, and then find out that I am trans, as something incidental to me rather than defining me. This is just my approach, though, I think it's personal to anyone. Personally I'm not going to be up front about something so personal with a guy I've just met - even if he's courting you after a month, that's no guarantee of any kind of relationship, he may just want fun, and talk sweetly to you to get what he wants, I think it takes a little while longer to forge a relationship where it's actually worth telling a guy (or girl, or whatever) about your past.