I can give you some advice on training that works in (almost) any area. :D
I usually train by Audino-hunting. In each town, there is a always a place near the town, either before, or around it. A patch of grass. Single-battle grass. I'll break this down into some steps:
• Find a patch of wild grass near a town, or where you need to battle to level up.
• Don't enter it yet! Find a long strip of land that you can ride your bike/run down.
• Continue pacing/biking until you see a shaky patch. Enter the battle.
• More times then not, Audino will appear. However, it is not guaranteed, and you should look at the site's route guide for all the possible Pokemon to show up.
• Lastly, do this as many times as you need to to reach the designated level. This method takes about as much time as battling a bunch of wild Pokemon, but it saves PP usages and in general, HP. Audino's moveset will alter with each route, but most of the time, it isn't to overpowering.
• Try to avoid doing this near water/caves. If you want to find Audino to train against, you'll need to do this only in the grass or else there is a possibility the shaking grass could actually turn out to be a bubbling water spot or a dust cloud.
• Try and Audino hunt near a location where a person can heal your Pokemon for free. These people that heal your Pokemon for free make it so you don't have to go all the way back to a Pokemon center. More to come later.
But for your specific problem, I'm actually in a very similar spot. I'm currently training for Skyla as well. :P Currently, I'm training my team of 5 up to level 45 for our battle. Currently, though, I'm still in Driftveil City training to level 40 before heading through the Chargestone Cave to Mistralton City to finish training. My Audino Spot for Diftveil is the single-patch of grass just before Chargestone Cave, not the double-grass. This spot is very shaky, Audino-wise, though, because the most common Pokemon that show up include Audino, Emolga, and Dunsparce, and more. In this situation, I go over to the double-grass every once-and-awhile because after doing some quick calculations, I can train 2 Pokemon for the roughly the same EXP gain as an Emolga. The house on this route can also heal your Pokemon, so this is a good area.
I know a lot of good Audino spots for anyone that wants to know, so don't be afraid to ask!