Head on back to the path, which turns West from where you ran off into the grass like a cat after a bit of floating dust, to a set of stairs that run up to some pipes.  You’ll want to check up there first.  Be careful as you run on the pipes- if you try to move in a direction the pipes don’t go, you’ll hop off- not painful, but it can get really inconvenient, forcing you to retrace your steps repeatedly.  Following the viable paths to the right you can come down some stairs to a worker who’s looking out on the ocean- He’s idling and thinking a bit, but when you challenge him, he’s willing to do battle.

Battle: Worker Isaac (480 Poke)
Opponent: Magby Lv 12, Koffing Lv 12

After the fight, he’s a lot more enthusiastic, so your job there is done- head down some more stairs to pick up TM 46 (Thief), which isn’t as useful as you’d like it to be... most of the time.  Using the Thief attack and having it come out better than a standard attack requires some particular conditions, so make sure you really want to actually use it before teaching it to any team members.

Clamber back up onto the pipes and head North so you can see the worker who was perched above the entrance gate of the complex.  He’s enjoying himself and his time with his pokemon, but accedes to a battle when you talk to him.

Battle: Worker Mitchell (480 Poke)
Opponent: Patrat Lv 12, Elekid Lv 12

Now enthusiastic about his work (if only because it will help his pokemon look their best), Mitchell gets down to it, so you can head along to the left across the pipes some more.  Follow the pipes to the end and you’ll reach a platform with a kid on it who wants to impress Roxie.  He’ll challenge you to battle so he can show his stuff.

Battle: Youngster Waylon (208 Poke)
Opponent: Patrat Lv 13

With everything overhead taken care of, it’s time to hop down off the side of the pipes into the grass- here’s the third worker, who is bored and takes the initiative, challenging you to battle!

Battle: Worker Nathan (480 Poke)
Opponent: Riolu Lv 12, Lillipup Lv 12

Beware of Nathan’s Riolu- while its attacks aren’t all too terrible to deal with, it packs the move Counter, which can do some ridiculous damage at this level if you don’t knock the Fighting-type out with the attack.  Once his two pokemon are defeated, he points out that things being the same means nothing has gone wrong, so he’s happy to get to work.  Your minor chore done, feel free to head on South into the complex- you’ll have to go see the guy who asked you for the favor on your way back out anyways.