I have been trying to find a good location to train my Ivysaur in SS somwhere where there are slightly stronger Pokemon (I had lvl.28 or lvl.29 Pokémon in mind) and a place where I wont have many type disadvantages because I want to evolve him quickly so that I can register Venusaur in the Pokedex. Note: location can be anywhere between the Jhoto and Kanto regions.
A good place to train is mount silver. You could switch ivysaur out to a stronger Pokémon, or have it hold an experience share.