I forgot to mention, that for every location you wish to have an encounter, you will need two encounter triggers. One including evil creatures (vampires, demons, skeletons), with the encounter faction set to evil. Another one including good creatures (women, men, vampire hunters), with the encounter faction set to good. Both of these triggers will share the same location. Therefore when a PC enters these triggers, the appropriate one will spawn creatures for the PC to fight.
For an example, a vampire enters the triggers. Since the vampire is evil, the trigger set to evil will do nothing, but the trigger set to good will spawn some goodie goodies.