We got the legendary dog whisperer leaving Madeo Restaurant in L.A. ... and he thinks it's time for Donald to fall in line with past presidents and welcome a dog to his family and the White House.

As for what type of dog ... the answer is pretty obvious to Cesar, and is definitely fitting for the Trump brand. Here's a hint -- it's the type of dog that has a good rep and makes life less stressful.

So ... definitely not a dog who might bite guests.