I was in Defcon this summer, it was amazing! The OpenCTF contest hosted there was very cool, give it a try if you have time. However, you must be aware that being less than 21 in Vegas and defcon could be problematic. In theory, you should be always accompanied by your legal representative in the casino, and that includes the con. But the con is still very cool, don’t worry (at least it was for me, and I am younger than you :p)
I hope I will be able to attend at least one French con this year, but not sure. If I do, I will be wearing a HackThis shirt so we can easily meet, if anyone is around.