Just check any currency converter and go down a little from there, depending if you are exchanging via bank (teller or ATM) and/or casa de cambio (street exchange booth)

Right now on :http://finance.yahoo.com/m5?a=1&s=USD&t=MXN&c=0
large amount of $ trading is 11.26, which means about 11.15 at the bank and about 11.00 or 10.90 pesos per US dollar on the street.

Have fun!