  The in-plane and out-of-plane magnetoresistance (MR) of single crystals of
La_2CuO_4, lightly doped (x=0.03) with either Sr (La_{2-x}Sr_xCuO_4) or Li
(La_2Cu_{1-x}Li_xO_4), have been measured in the fields applied parallel and
perpendicular to the CuO_2 planes. Both La_{1.97}Sr_{0.03}CuO_4 and
La_2Cu_{0.97}Li_{0.03}O_4 exhibit the emergence of a positive MR at
temperatures (T) well below the spin glass (SG) transition temperature T_{sg},
where charge dynamics is also glassy. This positive MR grows as T->0 and shows
hysteresis and memory. In this regime, the in-plane resistance R_{ab}(T,B) is
described by a scaling function, suggesting that short-range Coulomb repulsion
between two holes in the same disorder-localized state plays a key role at low
T. The results highlight similarities between this magnetic material and a
broad class of well-studied, nonmagnetic disordered insulators.
