[Rocky505]

The best place I've found to train is on the new route between Cianwood and the Safari Zone. You need Waterfall to get to the grass and the Pokemon are level 31-35.

What I do is find Dittos and let them transform into my Pokemon and KO them to get the most EXP. The Miltanks are also good to train on but they're hard to take out with physical attackers and will eat up the PP of your moves fast causing you to go back to a PC to heal.