Well, if you like to group (which I do) you can try Unrest or Mistmoore. I
personally prefer MM, but you will not be able to get any good items there
because you will be fighting the yard trash near the entrance. If you fight
in Unrest, you can get better items by pulling or camping deeper inside the
house. But, you will probably have to deal with the crowds of people. On
Tarew Marr, MM usually has about 25 people in zone, 45 at peak times when
higher levels decide to storm the castle. Unrest usually has 40 people min,
and sometimes goes well into the 80s. BTW, both zones count as outdoors, so
you can sing Selo's.

If you want to solo, you could try the Iron and Stone Guardians in Nektulos
Forest. The great thing about them is that any PC can outrun them, so they
are trivial to kite. I found them perfect for levels 19 to 21, but then
left out of boredom, not lack of experience.

Another spot you might like to try is Lake Rathetear. You can fight Aviak
Guards solo (look around) or you can group and fight at the Gnoll/Undead
camp during the night. And, just over the zone, you can fight all kinds of
Aviaks in South Karana.

Banilore Bel'Canto
22nd Level Half-Elf Bard
Master Brewer