Hello, when you are 5-23 mobs will drop linen, when you are 30-40 you get linen, and due to SM, alot of it. Lvl 41-50 you get mageweave, and sm cath/zf gives a lot of it. At the other hand, Wool cloth, has a short lvl range, and there's not too many instances that drop them in bigger quantities. As if that wasn't enough, to lvl tailoring and first aid you need tons of wool cloth. So guess what we want to farm in lower lvls?
Wool Cloth
To the spots!
Ashenvale, one word, furbolgs. They drop tons of it.
The Barrens, the dwarves at the excavation site.
The Stockades
Hillsbrad foothills, Durnholde keep.
Other spots: (mentioned by posts, I prefer the others though)
Worgens in duskwood, it works, but they doesn't drop as much and are a pain in the ass to kill imo.
Deadmines are another spot, the mobs tend to linen instead of wool half of the time(almost), but it works. The plus here is that you never have to wait for respawns and if you're a high lvl it's easy to mass the mobs and aoe them down. (cred to Xollax)
The quillboars in the barrens was suggested by Kingyoshi9, definitely a nice spot when questing. But I would say that you shouldn't grind there, there are just better places. =)
These are probably the best spots to farm it, they are there when you are lvling. Ofc higher lvls, 40-60, could farm there as well, with eez, and the money you earn is nice.
You might need some lvls for stockades.
Grind a lvl at one of the places and you will have enough money for epic mount when it's time =)