try 115200 as speed (i always boot my galileo with console=ttyS1,115200n8) and it works fine with my self-made cable.
but do you use 115200 when you are trying communicate for instance with a terminal console like Tera Terminal or putty (to test serial communication) or when you communicate by FTDI (ttySG0) to console linux?
Are you using the Galileo Gen1 or Gen2? In these links you will find which GPIOs you have to enable to use the UARTs for serial communication:
Try with the UART0 -> ttyS0
You can use 9600 as speed if your other device is using the same speed, also make sure all the parameters that you are using are the same in the other device (data bits, stop bits and parity)
Try sending the echo -e -n "\x12\x02" > /dev/ttyS0
When you are reading you only need cat /dev/ttyS0
I have already resolved the problem,
my USB-RS232 conversor had a problem sorry