I have it working in the I2C mode, but I was hoping to use the easier and faster SPI interface.
Why, if your carrier board does not work in SPI, do you describe SPI usage in your writeup (shown below)?
To communicate with the L3G4200D in SPI mode, the CS pin (which the board pulls to VDD through a 10 kΩ resistor) must be driven low before the start of an SPI command and allowed to return high after the end of the command. Level shifters on the SPI clock (SPC) and data in (SDI) lines enable SPI communication with microcontrollers operating at the same voltage as VIN (2.5-5.5 V).
In the default 4-wire mode, the gyro transmits data to the SPI master on a dedicated data out (SDO) line. If the SPI interface is configured to use 3-wire mode instead, the SDI line doubles as SDO and is driven by the L3G4200D when it transmits data to the master. A detailed explanation of the SPI interface on the L3G4200D can be found in its datasheet (1MB pdf).