Don't let the dragons teleport in your fortress :
An alternative to the rope trick : tight streets, tall buildings, long iron spikes everywhere in the sky above the buildings. Iron, because dragons are flying and after a first attempt where they only fly above your city while spiting fire, there are no ropes anymore. Then, knowing the place, they could teleport in the rope-less sky.
That's why a rich city could build some kind of a metal cage above the roofs, while a smaller city would only have spikes tied to the roofs. The cage could, or could not, have a way to hide the city (city-sized blinds ? I don't want to put the whole city in the dark every time, but there should be a way to open/close the city from the sky, like deploying sails on a boat).
For time travelling dragons, either you change the city aspect very often to confuse them or you keep it so unchanged frome the outside that no dragon can find a specific date to teleport at.
Make your land hard to find/recognise :
A nomad way of life could be quite efficient for common humans. Light and fast travel prevents teleporting dragons, either if they can travel in time or not.
With their big friends, dragonfolk would have some issues to keep a nomad life. I'm sure they want a big badass fortress. You can try to hide it (underground, underwater, under big trees of an ancient forest). You can cover it with mirrors (good luck to look inside, ennemy dragons !) or with another optical illusion. You can make your fortress move (may request a little magical help, but you have dragons. 160
They might pull a whole city if there are enough of them and the city is build with this trick in mind, on an artificial ground or something like that)
Oh my god, dragons are coming !
They did find your city ! What now ? If you have dragons too, of course, you send them. What else ? I assume that killing flying dragons from the ground is very hard. You can try to shoot at them with very big crossbows on the roofs (thanks <PERSON>), but there is 300 of them spitting fire, and they're going to target the crossbows first. I don't know if a dragon can be poisoned or drugged with these arrows.
If you're underground or underwater, let's hope you have trapped the entries. A sudden avalanche or a flood should switch their fire off. Nets falling into the passages could prevent them from flying properly. A bunch of projectiles (arrows, stones, dart) fired from protected nests in the passage would make their entrance difficult. Big wooden doors might not stop them for ever, but slow them long enough to make of lot of damages. If your entry looks like a galery, put spikes everywhere (spikes that can be easily installed/removed if you have dragons too.
And a last one : in the middle of the city make sure every street and every refuge access is far too little for a dragon, and eventually only humans would reach the critical point. 160