Apollovega, in most scenerios, no. You cant just telnet to any port, the telnet port itself is 23. If you telnet to a box it will most likely ask you for a password and maybe a username unless theres really nothing to telnet to.

Edit: Forgot to say, you can telnet to some protocols such as the HTTP protocol (port 80), or any other services you might want to access on any other port.