Is is possible for a microcontroller with a single serial output to interact with two serial peripherals?
Use/find/implement your own Arduino style software-serial library for slow baud-rate serial comms to one of the devices, and use the hardware UART (serial) to the other one. 

You could even do software serial for BOTH bluetooth and Xbee if data rates are kept low, and you dont have any crazy hard-realtime system (higher priority control) which may cause loss of data too often.