special spellings
 

I've seen x for por aki for aqui and kiero for quiero etc. How common are these spellings and are they acceptable?

they are SMS (phone message) spelling. Also valid for internet chat.
Not acceptable in any other place.

Another one I've seen is to2 (to-dos) instead of todos.

Muchas gracias a los 2.

salu2 (saludos)
to2 (todos)
t kiero (te quiero)
bs (besos)
x tí (por ti)
X --- Por
X ---( El sonido ch)
= --- Igual
Iwal --- Igual
Xo --- Pero
Xo --- Yo
XD --- Feliz
K --- Que
Q --- Que
Xk --- Porque
Aki --- Aquí
Sms --- Mensaje
N --- No/ En
T --- Te/ Tu
Ktl --- Que tal
Sts --- Estas
Nxe --- Noche
+ --- Más
(-) --- Menos
Ktepsa --- Que te pasa
S --- Es
Tkm --- Te quiero mucho
Mx --- Mucho
Bss --- Besos
1bst --- Un besito
L --- El
Asias --- Gracias
Wnas --- Buenas
Akbo --- Acabo
Gns --- Ganas
Cmo --- Como
Km --- Como
Dfcl --- Difícil
Mtt --- Metete
Dew --- Adiós
Ma --- Me a
Kt --- Que te
Sk --- Es que
Drmda --- Dormida
D --- De
diccionario
http://www.lonuncavisto.com/moviles/...o/abreviaturas

sal2 WMX :D

Wow! Cool, gracias por esta lista.

Is this the equivalent of english 1337 (elite) talk or is it actually commonly used?

I think leetspeak came out of the gaming community and is somewhat different from the sort of abbreviated words used for texting.