'Ello. PTR's are not up, but here is a little nice trick on how to get on the server you want.
Here is the list of servers on the PTR..
A = PVE server
B = PvP server
C = Rppve server
So you want to get on PvP server, first of all. Go on the PVE server and make the maximum level 1 characters you can till you cannot make any more characters on the PVE server.
Now got to Rppve server and repeat the same process, making the maximum level 1 characters possible on that server.
Now when you have C and A maxed out ( PVE and Rppve server)
Meaning you cannot make any more characters there.
Simply go to the WoW page and click transfer, it will now automaticlly transfer the characters you want to the PVP server.