Can you actually access mysql from any other host aside from localhost. By default mysql is only accessible from the system it is installed on. To allow access from other systems on your network, you need to modify /etc/mysql/my.cnf. Change the line:
bind-address = 127.0.0.1
where server-ip-address = the ip address of your server.
bind-address = <server-ip-address>
Note: it is not advisable to leave mysql open to the internet, as unless you are using a strong password, the admin user is already know in a default Ubuntu install, and it is just a matter of brute forcing the mysql password.