If you have installed a port and have changed your mind about the install options that are presented, 'make deinstall && make reinstall' will build the port with the same options that you already selected, without prompting you.
Can you change these options? Yes.
The options are stored in the options file in /var/db/ports/<port_name>/. Delete the options file specific to the port you wish to change, and you'll be presented with the same install options as when you originally installed the port.