I find it odd that i don't see many french speakers either. I run into them every once in a while and i get to test out my french skills which is either great or disappointing.
Honestly people shouldn't be complaining about spanish speaking players. It's a north american server.
I'm Canadian and I speak a little french because Canada is a bi-lingual country, we learn french from grade 4 (at least in toronto we do). America has a large hispanic population, certain states teach spanish in schools.
It should be expected to run into spanish speaking players when playing LoL.
If you see Russian then its a time to wonder what the **** is going on.