This is just like getting Attack EVs with Goldeen/Seaking, but you still need access to Kanto. There are some caves in Johto that have 60% chance of encounter for Geodudes, but I still found that a bit too low. This is the only place that I could find that had an extremely high encounter rate for a Pokemon that gives defense EVs, so unfortunately you have to have access to Kanto.
Route 42/Mt Mortar - 1F/ Mt Mortar - B1F If you do not have access to Kanto, then use the below spot. This is by far the easiest spot to train for Attack. This is best choice for HP, with low enough level and easy access.
Pokemon Name | EVs Given | Method of Encounter & Available Times of Encounter | % of Encounter | Level Min - Max All of the following hotspots work in both HG and SS. Luckily for us, HGSS has at least 1 amazing hotspot for each stat. For this reason, this list of EV training hotspots is all about Wild Pokemon. With the lack of the VS Seeker in HGSS, we lost a reliable way to rebattle trainers.