Route 1 is the best place to EV Train in Attack specifically on Patrats and Lilipups. Hope this helps...
You can find muscle wings on the driftveil and marvelous bridge to raise attack evs.
The best place in my opinion is the 1f Dragonspiral tower, north of iccirus city. it has only mienfoo (1 atk) golett (1 atk) and druddigon (2atk) all between level 30 - 40. if your pokemon are not strong enough to fight them, then route 1 has patrat and lillipup (1atk ev) but beware for audino in shaking grass :D