Lexicon

The following is a near-complete index of words that fluffy ponies should know by default.  Which is to say, they should know these words without being taught by a human or another fluffy.  Even fluffies taken from their mothers immediately after birth and raised without human speech know and can correctly use these simple words.

A: Alone, Apple, Away
B: Baby, Bad, Ball, Better, Big, Blocks, Boo-boo, Bright, Brother, Box
C: Cold, Come
D: Daddy, Dark, Down, Dumb
E: Eyes
F: Face, Fast, Feel, Fire, Flower, Fluff, Fluffy, Fly, Food, For, Forever, Forgive, Friend
G: Game, Get, Give, Go, Good
H: Happy, Hate, Hello, Help, Here, Hoof, Horn, Hug, Human, Hurt.
I: Itch, Icky, Is
J: Juice, Jump
K: Know
L: Leave, Legs, Like, Litterbox, Love
M: Make, Mean, Milk, Mommy, Monster, More, Move
N: Name, Nice, No, Nose, Not, Now
O: Ow, Ouch (possibly "only")
P: Pee-Pee, Place, Play, Poop, Pretty
Q: ???
R: Really, Run
S: Sad, Safe, Say, Scared, Scary, Share, Sleep, Silly, Sister, Smart, Smell, Soon, Sorry, Spaghetti, Special, Stomach, String,
T: Tail, That, This, Time, To, Too (possibly "These" and "Those")
U: Up
V: ??? (Possibly "Very")
W: Warm, Water, Wings, with, What, Where, Who, Why
X: ???
Y: You, Yummies
Z: ???

Some common calls of the wild fluffy pony:

In their territory:

"Smawty fwiend sai dis fwuffy pwace!"
"Gud foodies hea!"
"Dis saf pwace."
"Fwuffy nee poopies!"

Afield:

"Whea fwuffy?"
"Fwuffy tummeh ouchies, wan nummies."
"Nuu saf hea, smeww munsta!"
"New fwiend?"

Expectant Mothers:

"Wai weggies nuu wun?"
"Fwuffy nee hewp!  Nuu move!"
"Babbehs com soon."
"BIG POOPIES COM!  Fwuffy nee hewp!"

Around their nest:

"Mommeh wuv babbeh."
"Mommah haf miwk foh babbeh."
"Babbeh saf hea, Mommeh geh foodies foh moah miwk."
"Babbehs siwwy!"

In conflict with each other:

"Go 'wai bad fwuffy."
"OWIES!  Wai meanie smawty gif nose ouchies?"
"Boo-boo Juice mae fwuff nuu smeww pwetty..."
(A sound that can only be described as two toddlers blowing raspberries at each other)

When confronting predators:

"Go 'way meanie munstah!"
"Mae munsta sowwy wif sowwy poopies!"
"Munstah!  Wun!"
"NUUU!  NUU HUWT FWUFFY!  WAI OUCHIES?"