SQL Server store procedure encrypt is safe

The default instance uses port 1433. Named instances will use dynamically negotiated ports (but can be configured to listen on specified ports-- see http://msdn.microsoft.com/en-us/library/ms177440.aspx).

Edit:

By default when a named instance of SQL Server starts it chooses a randomly unused port and registers that with the SQL Browser service. Clients send requests to that service (UDP port 1434) to retrive the port number for the instance they're trying to connect. You are correct in that the dynamic port number will remain the same throughout a single execution of a given instance. If you stop / restart that instance, though, the port number will change. So, there is no "fixed" value for the dynamic port.

It is possible to decrypt and view the source of encrypted SQL stored procedures, a quick search for "Decrypt sql stored procedure" shows you a fair number of hits, for example:

http://www.mssqltips.com/tip.asp?tip=1046

However encrypting your stored procedure does at least make it more difficult to see the source - I'm also not sure whether any of the current methods of decrypting stored procedures are actually viable on a live SQL server installation - last time I looked many methods required exclusive access to the SQL server instance, and prevented any other users from accessing the server (although this may not still be true).

Its also worth noting that encrypting your stored procedure can raise support headaches - because you are no longer able to see execution plans for your encrypted stored procedures you may have problems attempting to diagnose any performance issues.

I'm not aware of any other method of protecting your source.