I recommend you to check the following thread: Using Galileo Linux over Ethernet(Telnet). That thread explains how to access the Galileo's terminal using Telnet (through the Ethernet port). This way you would be able to access the terminal without the serial cable.
Regarding the serial cable, in the following site there is a quick guide about building a serial cable for Galileo: Intel Galileo - Introduction - Malinov Family Web Presence. I recommend you to check that site, you might find it interesting.
Regarding the Galileo board that appears as "device", I recommend you to check if the drivers are installed properly and the board has the firmware upgraded. You can upgrade the firmware using the Firmware Updater Tool which is available in the following site: Download Intel® Galileo Firmware and Drivers 1.0.4