Did japanese people (Civilians, military personnel, politicians) of Hiroshima and Nagasaki knew about the atomic bombs during WW2? If so did somebody evacuate or escape?

If you're asking, "did they know, or were they warned that they were atomic bomb targets?" the answer is a decisive "no." There are many threads on this forum about this (searching for "warning leaflet"), but here is one that addresses evacuation specifically a well.