No, you cannot join Team Galactic in any of the official Pokemon games.
Shoot
The Galactic grunts are just members of Team galactic. They don't have a high rank like Mars or Saturn.
Why would you want to give Team Galactic your Pokemon? Anyway, you can't.
The Galactic Grunt in Pastoria City has it. You need to bet the Gym to get it.
When you go to the team galactic veilstone building there will be a galactic grunt and you talk to him then he'll run away and he accidentally drops a key.
You can't
To get into the Team Galactic HQ in Pokemon Diamond you will need the storage key the Galactic Grunt leaves behind, and the Dusk Stone. If you can't get the key, it may mean you have not completed a mission.
I don't think you can join team galactic and if you can, I'm giving you bad advice! I don't think you can join team galactic!
da talk to him
You can't join
No.
You may not join Team Galactic in Pokemon Pearl or Diamond.
the Pokemon champion Cynthia gives it to you after you chase the team galactic grunt to lake valor