I have often seen school children in the months of monsoon i.e. June-August picking berries along the way to school.... when we were in Mcleodganj roaming the surrounding villages one could find them all over the place... It would be very easy to spot them in a few days since the flowering season of Berberis has already begun in the lower altitudes of Chamba region (and so it would be in D'sala)... you cannot miss the thorny bushes with the bright yellow flowers... :)
And you needn't worry about finding a botanist ... since there are many a member of this group who has roamed around these hills too and with people like Gurcharan ji... most of the Himalayan plants are easily identifiable...
Alok