Diglett's Cave for Speed (Diglett+Dugtrio), surfing on the Mount Mortar lake for Attack (Goldeen and Seaking). For special attack, I generally use the ruins of Alph's little grassy patch, for Natu and the occasional Smeargle.
I need good spots for SP. Def and HP, though, as well as DEF.
HP: Surf at the Cliff's Edge Gate; 90% chance of finding Wooper (1 HP EV), 10% chance of finding Quagsire (2 HP EVs)
Attack: Surf at Mt. Mortar; 90% of finding Goldeen (1 Attack EV), 10% of finding Seaking (2 Attack EVs)
Defense: Tall grass at Route 2; 90% of finding Tangela* (1 Defense EV)
Special Attack: Surf at Route 35; 90% of finding Psyduck (1 Special Attack EV), 10% of finding Golduck (2 Special Attack EVs)
Special Defense: Surf at Routes 40 / 41; 90% / 60% chance of finding Tentacool (1 Special Defense EV), 10% / 30% chance of finding Tentacruel (2 Special Defense EVs), 10% chance of finding Mantine (2 Special Defense EVs)**
Speed: Diglett's cave; 90% chance of finding Diglett (1 Speed EV), 10% of finding Dugtrio (2 Speed EVs)