That's a lie, there is a Battle Tower in Leaf Green/Fire Red though I'm not sure if the prizes are worth much. And yes ya can EV train though I would recommend later when you got better Pokemon to choose from.
There is a facility that is like a Battle Tower in FRLG but unlike one, items can be used in and between battles and Pokémon cannot be healed between battles. It's more like Trainer Hill in Emerald than the Battle Tower in RS and the Battle Frontier in Emerald.
So I guess what I'm not understanding, is if I don't plan to play for 100% top line pokemon;
A) Does it really matter.
B) How do I get perfect EV's while leveling the first time to beat Elite Four?
A) It doesn't really matter what EVs you give to your Pokémon and you can still beat the game without giving your Pokémon specific EV spreads.
B) To max out a specific EV, assuming you will most likely won't have the Macho Brace by then, it will be good to buy Vitamins for a stat you want to EV train. Vitamins increase a specific EV by 10 points until it reaches 100. But your Pokémon may have gained some EVs already at that point from battling Trainers and wild Pokémon and they may as well be over 100. Unfortunately you won't be able to get EV reducing Berries in the game if you don't have a GBA Wireless Adapter because these Berries are only available as prizes in the Dodrio Berry Picking game and you would already have to have beaten Blaine if you want to get to the Joyful Game Corner, which is at Two Island at the Sevii Islands. And you won't be able to trade with Ruby, Sapphire and Emerald until you beat the game. So if you don't have a GBA Wireless Adapter, before beating the game, it's impossible to reduce EVs in the game.
But it's still possible. Each species of Pokémon have a specific EV yield so this means if you defeat them your Pokémon that were in battle against that Pokémon will get a certain amount of EVs from that Pokémon so let's say if your Pikachu defeated a Pidgey your Pikachu will gain one EV point in Speed. And if you battle against Pidgey again with Pikachu and you switch into Charmander, if either Pikachu or Charmander defeat that Pidgey then both Pikachu and Charmander will gain 1 Speed EV. But Pokémon have a variety of EV yields there's a good amount of Pokémon to choose from. Pokémon tend to give out 1, 2 or 3 EVs in a specific stat.
EVs in FRLG cap at 255 for each stat so the maximum EVs you can have in a stat is 255. The total EV, which is the amount of EVs when you add your Pokémon's EVs together, caps at 510 and once your Pokémon has reached that total, it cannot gain any further EVs. So technically at most you can have two perfect EVs. But I advise you to train to 252 for the two EVs you want to max out and use the rest of the 6 EVs on some other random stat so no EVs get wasted.
You can keep on battling a specific species of Pokémon until you get to 252. More rarely, you may get the Pokérus on your Pokémon and it doubles the amount of EVs your Pokémon gain.