iPhone in Mexico (Telcel)

[elmonquis1219]

I know they sell the iPhone in Mexico with Telcel as a carrier, I have a 3G (Version 2.2.1 and Modem Firmware 02.30.03) Does anybody knows if I have to unluck my phone in order to work with the Telcel Network in Mexico. I'm planning to go for a couple of weeks and I would like to get a local number there (Telcel SIM Card). If I have to unluck it what program do I have to use, I don't want to upgrade to the new Version (3.0) because I have the unlimited data plan for the regular phone not for the smart phones ($15/ mo) and if I upgrade to the 3.0 the internet woldn't work. ANY HELP WILL BE APPRECIATED. THANK YOU IN ADVANCE.