I read this in the early nineties, and it was set in an England which had been flooded due to climate change, and the humans had fled as a result. A group of animals, who can communicate with each other, read road signs to try to reach London Zoo where there is a group of intelligent apes or maybe monkeys. They have to travel by boat. One of the characters was a dog named Pal.
I've had no luck finding it, I'd be grateful if anyone recognises the description.