There is a spot I just found that could contain good ore. I've been making really big underground passages to find some good ore. The spot I found has monsters in it. If I kill the monsters and put torches where I killed them and where they started off at, will they still respawn?
Monsters can spawn wherever there is darkness. However, if there are (I forget the exact number) 3-5 of the same type romping around, you are probably near a dungeon, and should be wary because dungeon monsters DO respawn. Kill the monsters, then search for naturally found cobblestone or mossy cobblestone to take out the spawner.
So no.