It is a bit of detective work, as no example is given to turn off the priority registers to get your digital I/O (some data sheets do).
So starting with the priorities given in the GPIO section, go to the memory organization section which has a special function table of the register,bit values based on a power-on reset. Hidden in the OPTION regsiter description you see that T0CS(T0CK1) affects the TRIS function of GP2. On reset T0CS is set, so try clearing OPTION,T0CS.