As Cen said, Unrest can be a good spot to find a group at 20.
Other possible group places:
-upper guk near the zoneline to lower guk
-mistmoore pond area
Good solo spots if you cant find a group:
-charming deepwater gators in oasis (good through 22 or 23)
-charming in Overthere along the East zone wall north of the warsliks woods zoneline (can charm tigers and rhinos to kill sarnaks, cactuses, and cockatrice)
-root/rotting giants in warsliks giant fort, though might be better starting around 24, use harmony to pull singles (can possibly form a group here if you see someone soloing)
-charming mammoths in Everfrost peaks (may be more like 24+, it's been a while)
Another option is questing. Taken from the
Per-Level Hunting guide, You can repeat the
Slaythe portion of
this quest if you are at least indifferent with the rivervale rogue faction. If not, then it's doable after 24 with wolf form.