The Internet has spoken!
If Goku could have just teleported to the world of the living at will he would have done so after Buu absorbed Gotenks and Piccolo and started owning Gohan. The stakes were certainly high enough and Goku was desperate enough that he would have done it if he could, rules be damned. This isn't Team Four Star Goku, he's not going to let his son be killed just because someone said it, "wouldn't be nice." The fact that Old Kai had to restore Goku to life seems to suggest that 'porting to the living world while dead can't be done, at least not with Goku's teleportation. The only time we see Goku go to Earth while dead without permission is in the Bojack movie, which is basically filler, even though it's one of the few movies that fits comfortably within the manga and anime's timeline. Even then, to Bojack, Goku was there just long enough to punch him in the face and make him release Gohan. From Gohan's perspective, he was there long enough to punch Bojack, carry him safely to the ground and give him a cowboy speech. So that whole moment is filler, on top of being more than a little confusing on what exactly happened. So yeah, I'd say everything the main cannon suggests says Goku can't teleport to any place in the world of the living while he's dead unless someone with particular abilities, like King Yema or Baba, grants him permission.
Interestingly, this would suggest that his teleportation is much improved while alive, since there's nothing suggesting a living person can't go anywhere he wants with the instant movement, as long as he can lock on to a bit of chi.
On topic, my only real experiance with Nova was in old New Warriors comics where he was nowhere near Goku's level. If he's rubbing elbows with the more space faring and cosmic level characters he's probably gotten a signifigant upgrade. Still, nothing I've heard of or read in this topic at least suggests he'd beat Goku at his best. Someone feel free to correct me if I'm wrong.