This shows how to tar the current directory except the unwanted subdirectory files.
tar cvpzf backup.tgz --exclude='dir_to_exculde/*' *
tar cvpzf backup.tgz --exclude='dir_to_exculde/*'
--exclude='dir_to_exculde' *
//The last asteric means that the current dir is used. Keep in mind that files with a dot aren't included.
//The secound example excludes also the directory from being included otherwise it would be included as empty one...