Gnomes are absolutely welcome in Ironforge! They just moved out in Cata because it was a temporary arrangement - they lived in Gnomeregan before the radiation bit, King Magni just offered them a place to stay until they could figure their home out! Even so, Tinker Town in Ironforge still exists. Gnomes are the oldest and greatest allies of the dwarves, and are generally well regarded by the other races of the Alliance. The only groups that would really dislike the gnomes would probably be goblins (which is more of a love/hate relationship) and vaguely the Horde as a result of the gnomes being in the Alliance.
On that note, the Mead Hall community (which is dwarven) is open to everyone but especially gnomes, since gnomes are our best buddies and literally helped make Ironforge, steam tanks, gyrocopters, etc. We even have a little band of slightly chaotic gnomes that we run events with! We are not gnome-centric but since gnomes and dwarves are historically inter-connected we do all sorts of things together!
You can check out the Mead Hall through this post.