hi,
for rx and tx you don't need to bypass anything as far as i can tell. as Mellis said, digital pin 0 and 1 are marked rx and tx. all data you send through the serial interface does flow through your usb-port to your computer and at the same time through the tx-pin. incoming data is read both from the usb port (coming from your computer) or the rx-pin on arduino.
this should be true as long as you don't assign any other function (digital in or out) to those pins.
(SPECUALTION AHEAD!)
as for RTS and CTS (ready-to-send/clear-to send) on your bluetooth module you can just connect them to each other i guess. those lines are used for flow control, i.e. to signalize that a device is ready to send or receive data. if you experience problems you might bypass/grab those line from somewhere on the board. maybe someone more familiar with the board will help you then.
see
http://en.wikipedia.org/wiki/Serial_port >>>"flow control" for more info.
AND someone correct me if i'm wrong please!
please post your results here! i'm thinking of going bluetooth too.
best,
k u k