http://www.gamefaqs.com/portable/ds/file/925601/45193
EV Training Hotspot are below.
EVs: Location (Location description, Pokemon/Family [EV quantity apiece], run from unrelated pokemon)
HP: Route 201 (Bidoof [1], run from Starly), Windworks Valley (Shellos [1] and Bidoof, run from all others) and Route 222 (Gastrodon ONLY [2 apiece], run from everything else)
Attack EVs: Route 212 (Kricketune [2] and Bibarel [2], run from everything else)
Defense EVs: Iron Island Mines (Geodude family [dude 1, gravel 2] and Onix [1], run from Zubat Family)
Special Attack EVs: Old Chateau (The haunted house in Eterna Forest, Gastly family [Gastly 1, Haunter 2 *GBA SLOT*, Gengar 3 *GBA SLOT*])
Special Defense: Any SEA ROUTE (Tentacool Family ['cool 1, 'cruel 2], run from everything else)
Speed: Ravaged Path (that cave between Jubilife and Floroma, Zubats [1], run from Geodudes (if on land) and Psyduck (if surfing))
Have better EV training spots in Sinnoh? Share them in this thread.
Want to use this info in a FAQ? Go ahead.
Note: Haunter and Gengar apparently show up in the Chateau only if there is an ADVANCE Generation Pokemon cart in the GBA slot.