Hello! Welcome!
I too adopted a galgo recently. He's been home almost two month. He came from Fundacion Benjamin Menhert in Seville.
Do you know anything about Jersey's background? Was he mistreated before he went to SOS Galgo? It's very possible that he was traumatized.
My galgo, Iker, was traumatized and also spent six months in a foster home. He made great progress, but I'm pretty sure he's had several setbacks since I brought him home. I've been using lots of positive reinforment with Iker. I would leave a trail of stinky treats to get him used to doing things he didn't want to do, such as go outside. Maybe you can try the same to get Jersey to the main floor. You can also give him treats after you get him in the main room. Treats have made all the difference in the world with Iker. If you find Jersey is nervous about taking them, you can kind of toss them to the side. It seems like you've been doing that, but keep it up. Maybe try new treats if the current ones aren't working. I couldn't find anything that worked until somebody gave me homebaked liver treats. They work like a charm.
Maybe you can bribe him to go downstairs for his meals the same way. Another thing you can try is feeding him where he's comfortable, then gradually moving his bowl downstairs until he gets used to it.
I agree that it might be kind of soon. Relax, find some good treats, and don't pressure him. He'll come around.
Hopefully with the right treats, you can get him to come downstairs. Who knows what his past was like, and if he's known horrors before he ended up at the shelter.