This was posted on some thread but I forgot where, luckily I saved a copy of it so here it is:
HP:
Route 209 - Cowgirl Shelley - L14, 15, 15, 15, and 16 Bidoof (5 HP)
Route 210 - Bird Keeper Brianna (lower level) - L38 and 42 Noctowl (4 HP)
Route 212 - Fisherman Travis (bottom) - L17, 17, and 18 Barboach, L20 Shellos (4 HP)
Route 213 - Tuber Jared (pacing) - L52, 53, and 51 Gastrodon (6 HP)
Route 219 – Tuber Mariel – L29 and 29 Marill (4 HP)*
*Not recommended because she’s on a very small island with confined movement. But hey, at least the Route 201 music there is cool. Really has that "Route 1" nostalgia from the first time anyone battled a Pidgey in R/B.
*Turismo2029 notes that Brianna's Noctowl can hit level 60. See if it works for you.
Attack:
Route 203 - Lass Madeline (upper area) - L38 Staraptor, L38 Bibarel (5 Attack)
Route 213 - SwimmerM Sheltin - L30, 29, and 31 Gyarados (6 Attack)**
Route 214 - PI Carlos - L36 Goldeen, L37 and 38 Seaking (5 Attack)
Route 218 - Fisherman Miguel (bottom) - L53 and 53 Gyarados (4 Attack)*
Route 222 – Fisherman Alec (leftmost) – L53 and 53 Gyarados (4 Attack)*
Route 225 – Ace Trainer Quinn (standing still) – L53 Pinsir and L53 Mightyena (4 Attack)**
*The pro to training with Miguel over Alec is that he's also next to Fisherman Luc (4 Speed, 2 Attack), so you can train two stats at once. The con is that you only have 3-4 spaces to move to recharge the VS Seeker.
The pro to training with Alec over Miguel is that there's more room to move, and he's also within range of Rich Boy Trey, who has a L55 Luxio (2 Attack) and gives 8800 without Amulet Coin/Luck Incense. (Note: Firestorm88 says Trey hits L60 eventually and gives 9600.) I don't see any downside to Alec. Unless you're really interested in training Speed and Attack simultaneously, but Speed is the easiest stat to do.
**Getting to Quinn involves traveling through lots of grass and getting to Sheltin involves traveling over water, so I don't recommend it (even though there's a bit of land near where Sheltin is, you'd still have to be using Surf on and off to recharge).
***Ortega (on Smogon) says PI Carlos' Goldeen becomes a Seaking, meaning Carlos would give 6 Attack (not counting Macho Brave/Power items/Pokerus). And Twinks9999 and Juuka both say that Cyclist John on Cycling Road (third male from top) gets two Staraptor, which would also give 6 Attack. I can't get either of these evolutions to happen, so see what happens for you.
Defense:
Route 210 (tall grass area) - Ninja Boy Fabian (middle) - L23, 23, and 26 Geodude (3 Defense)
Route 212 (rain area) - Collector Dominique - L17, 18, and 19 Geodude (3 Defense)
Route 221 – Collector Ivan – L51, 52, and 53 Hippopotas (3 Defense)
Training Defense will be slightly annoying no matter which of these trainers you pick. Fabian's in tall grass, Ivan will have Sandstorm going every turn, and Dominique is in the rain--so you won't get hurt every turn, at least, but biking to recharge has a little slowdown. I tend to use Ivan.
Special Attack:
Route 212 (rain area) - PKMN Ranger Jeffrey (northwest end) - L21 and 21 Prinplup (4 Sp. Attack)
Route 212 (rain area) - Scientist Shaun (need Cut) - L53 and 53 Alakazam (6 Sp. Attack)
Route 214 - Psychic Mitchell (spinning, pacing) - L38 Haunter, L42 Kadabra (4 Sp. Attack)
Route 214 - Collector Douglas (south end of split paths) - L20, 22, and 24 Roselia (6 Sp. Attack)
Not much to say. Special Attack is very easy to train, and the Pokemon are weak against just the sorts of attacks that most special sweepers would use--Electric, Grass, Ghost, Psychic, Ice, Fire. Douglas is the best if you're using the Power Lens since he has a team of three, but the others are fine if you have no Power Lens, or if you're running a team with 5 Pickup users and want to fight fewer Pokemon before checking for Rare Candies, Dusk Stones, etc.
Special Defense:
Route 210 (foggy section) - Ninja Boy Davido (upper level) - L27 Dustox (3 Sp. Defense)
Route 230 – SwimmerF Sophia (bottom of pair with SwimmerM) – L50 Mantyke, L52 Mantine (3 Sp. Defense)*
Route 230 – SwimmerF Mallory (pacing, spinning, in the top "row" of rocks) – L50 Seel, L54 Dewgong (3 Sp. Defense)*
Surfing is obnoxiously slow and you'll need repels, but at least Sophia is next to a SwimmerM Sam with Chinchou and Lanturn (for 3 HP). Could be a semi-decent place to go, but I wouldn't. And don't even bother with Mallory, who's farther into the same route. I'm just recording her for the sake of it.
Speed:
Route 205 (water bridge section) - Fisherman Andrew (second from right) - L10, 10, 10, 10, 10, and 10 Magikarp (6 Speed)
Cycling Road - Cyclist John (third male from top) - L37 and 39 Staravia (4 Speed)
Easiest stat to train ever. In some ways, I might recommend training with Andrew for any stat with the help of the Power items (particularly for Defense and Special Defense) and just planting a lot of Tamato Berries to get rid of Speed gains when you don't need them. The experience sucks, of course, which is where John is a decent alternative (that and, again, Pickup abuse), but at least any Pokemon can fight Andrew without help from Exp. Share and such.
*Twinks9999 and Juuka note that John's Staravia evolve into Staraptor after a while, which would send them into the Attack section (6 Attack) and leave no Speed alternatives to Andrew. They're not doing it for me, so test to see what's the case on your game.
