Since a couple of the creatures can't always be relied upon to be hanging around waiting for you to kill them at need you'll probably prefer to take a few steps just outside the Smokestead gate to the very beginning of the Old Duke's Estate just to save time. I have checked, though, and you can get both the Moa and Harpy kills while standing behind the gate itself, so they count!
It's also very easy to do Daily Events here and I may do a separate pictorial guide to that at some point. For Daily Healer you'll find plenty of Fishers lying down on the job at Lake Feritas and the Armory and Scrapyard events leave flattened charr NPCs strewn all over just waiting for you to soothe them back to life. Gatherer is possible, although its not the easiest place to do it. Kill Count you can do anywhere, of course, and I guess you could Dodge something here although I haven't tried. Crafting and the Laurel Vendor can be done in Black Citadel, which sort of counts, maybe, but for Aquatic and Veteran Kills I'm afraid you'll have to just hike up your robe and travel a few hundred yards into Plains of Ashford proper.
And with that, here's the guide:
You'll see these ubiquitous little pests as soon as you come down the ramp from The Black Citadel.
In Plains of Ashford you're never more than a few feet from a rat. The Scrapyard teems with them.
Thanks to the legacy of the Foefire, nowhere in Plains of Ashford is entirely free of ghosts, although the infestation here is mild. Try along the west side of Lake Feritas or up on the ridge near the tunnel to Martyr's Wood.
Lurking at the back of the Scrapyard (or wrecking yard if you prefer) you'll find plenty of these bile green gloops. Wear a rubber apron.
Don't bother him, he won't bother you. Hyenas pad quietly through the scrub in front of Black Citadel and around the lake.
Like the good old Moa, for example. For these you have to step just outside the Smokestead gate, where you'll see a pack (herd? flock?) of them careening up and down in that mindless way they have.
I'm not sure why the kill variety requirement was reduced from the elegant fifteen to the rather awkward thirteen. Just in case it ever reverts, never fear! You can still finish it here, although you will have to take just a few paces out into the wider Plains.
Harpies swoop in for an event that runs regularly even with no player involvement. It takes place immediately to the left of the Smokestead gate as you leave it, right where the mortars are.
If anyone knows of anything else lurking in the area that counts, please chirp up in the comments and if I can get a photo of it I'll add it in.