Here is a map with all currently known spawn points of the Edge of Reality portal in Frostfire Ridge.
This screenshot from a user shows a spot where you can keep watch on all 3 known portal spawns:
|All 3 portal spawn points|
/ way 51 19.8 Ramp (bird)
/ way 52.5 17.8 Rylak
/ way 53.8 17.3 Trees
I didn't write down the names of the people who took the screenshots, but feel free to let me know if you want your name added etc. I will also do my best to add names when I find them again. All the ingame pictures are from wowhead.