Do they sell trees there? Specifically orange trees?

Not sure if there are orange trees, but definitely lemon trees. Check the gardening section behind the food trucks.

I am 100% sure trees are sold here but I cannot be certain you will find orange trees. I'd bet the vendor who has trees could tell you if and when you could get them there. Hope this helps!

Yes

They do sell some in the summer but I'm not sure about oranges specifically

During the summer various vendors do sell trees. I cant guarantee they sell orange trees though. Your best bet would be to call them and check.