Just try to relax *hugs*
There are quite a few people who don't tell right from the start because they want a chance to be seen as who they are as a person.
If you do not make a big deal out of it its more likely they react in kind.
You might tell that there are studies showing being transgender is biological, to do with development before birth.
So its literally a girls brain in a mans body and vice versa.
http://www.gires.org.uk/assets/DOH-Assets/pdf/doh-transgender-experiences.pdfThe usual remedy is to adapt the body, which is possible with hormones.
So the body is the real deal... and they are attracted by femininity.
You might test the waters by asking how they stand in lgbt issues.
Maybe asking about a movie or a series. But it might just give a hint.
Wish you luck ... if they really like you its possible they come around.
I'd say consider your safety when doing it .. one option might be over skype for example...
or as you said in a public place.
many *hugs*