I believe you have to have ethernet access anyway because with serial you still need to load u-boot image over tftp. You either need a jtag or get an Ethernet to WiFi bridge (or make one with help of dd-wrt with any supported broadcom router). I don not know how to jtag it, and from past experience with other hardware it will be difficult. My recommendation is to get the Ethernet to WiFi bridge.
Edit: you can setup your computer to share wifi connection.
If you still want to go serial/tftp way:
http://forum.doozan.com/read.php?3,6965