On the foggy part Route 210, there's a range of Pokemon to help EV train:
Bibarel +2 attack
Hoothoot +1 HP
Noctowl +2 HP
Meditite +2 speed
Machop +1 attck
Machoke +2 attack
Scyther +1 attack
Swablu +1 sp. def
And if you want defence EVs, you need to go forwards to Mt. Coronet and battle Geodude, Bronzor and Nosepass, but all for a measly +1 defence EV.
Walkthrough and EV list
Having said that, you don't need to EV train Pokemon for in-game battles, nor should you. While you might think that you're hitting two birds with one stone by EV training while playing the game, it's too hard to keep your EVs right since you will meet wild Pokemon. If you run away from all those battles, how long is it going to take you to get through one gym.
The most important reason not to EV train is that you will gain EVs from gym/ trainer battles, something that you have no control over since you have to complete them.
