|You should use SSH.|
W/ SSH you can create tunnels to forward other connections through your SSH session. It's also encrypted, and works as a file transfer program. There's really no reason to use telnet unless the device you're using won't run SSH.
That said - if you really want to run telnet, and you don't want to use a Proxy / VPN / SSH Tunnel, you need to forward different ports on your router to the local boxes.
So, on your router, make incoming 23002 forward to 192.168.0.2:22, 23004 -> 192.168.0.4:22, 23150 -> 192.168.0.150:22, etc. Then from the outside: telnet <public ip> 23004
But, an SSH tunnel is a much better solution.