I suppose you could, the TIP-120 seems to have good enough ratings for it.http://www.learn-c.com/tip120.pdf
Pay attention to the pinout, make sure you have a resistor between arduino pin and the base pin, a minimum of 220 ohm should be safe. Try that, measure the voltage across and calculate the current out of the arduino (V across the R)/R = current. Find an R that keeps it around 20mA, maybe 30 if your motors aren't going full speed. You can measure it directly if you have a multimeter with a mA setting; put your meter in series with the arduino output and the resister.
You might want to put a heatsink on the transistor (bolt a bit of metal to it to help dissipate heat).
Not sure what you'd do with 2 motors spinning in unison ...