Yoda knew that Palpatine was simply TOO powerful for any Jedi other than someone with the same midi-chlorian count as Anakin, to take on.
Yoda had to wait for Luke to grow up and for the force to create the circumstances necessary to bring Luke to him for training, when the time is right. Training any other Jedi would have been a waste of time. He also knew that there were several dozen to perhaps a hundred or so Jedi that survived order 66, but that they were told to go into hiding, abandon being a Jedi and live as normal a life as possible.
Yoda had no way to search out for new Jedi students while he is in exile on such a remote planet as Dagobah. The other reason that Yoda picked Dagobah is because he had once fought a very powerful dark Jedi on the planet and defeated him there. That is the source of the poweful concentration of dark side energy in the cave where Luke failed and such the vision of Darth Vader that ended up being Luke himself.
When Yoda killed the dark Jedi, the explosion of dark side energy infected the cave, which is why Yoda brought him there as a test.
Yoda's small hut was only a short distance from that dark side cave.. this was not by accident at all. Yoda specifically put his house there because he knew that with such a strong nexus of dark side energy there, it would hide his powerful light side force signature from being picked up by Palpatine or Vader.
Luke later surmized that it was like a positive and negative charge that cancel each other out and this was a major reason why Yoda was able to stay completely hidden from Palpatine the entire time. That, along with his natural ability to hide in the force as well.