Congrats! I had to wait until I was 18 weeks to find out my first was a boy :) But it also depends on your doctor( and insurance), some like to wait until 18-20 weeks to be sure, but others will do a U/S at 15 weeks. My doctor wanted to wait so my baby would be a little larger since that was the last U/S until 31/32 weeks. But good luck and I hope you find out sooner than I did for my first, I can't wait to find out the sex of my second! :)
I think that it depends on the equipment, the technician, and how cooperative your baby is :) With our first we found out is was a girl at 15 weeks (we ultimately ended up miscarrying that pregnancy though). But, in general... 14-15 weeks is pretty early. I would love to know what I am having in a week or two!! I think that we are going to have to wait until 18 weeks though.