Will work on 3g speeds IF and only IF your cellular phone operator/provider company offers that service IN the frequencies that the N900 has builtin.

In other words, for instance, there is no N900 version (at least as of Dec 31, 2009) that supports UMTS 850/1900 to be used on a 3g network in Mexico City (which happens to be the same as AT&T frequencies for 3g in the USA).

My 2 cents.

P.S. Nokia, hopefully there will be an N900 version with these 3g freqs !