De acordo com o “Guia prático de verbos com preposições” (o que é muito bom para ler se não conseguir dormir) -
Falar pode tomar as seguintes preposições:
Falar Com (speak with)
Falar Por (Speak for/on behalf of)
Falar A (Speak to)
Falar De (Speak of)
Falar Sobre (Speak about)
Falar Em (Speak about/mention)
Falar Para (Speak to/call - as in to telephone)
@pwsteele, as @samarang listed, several prepositions can be correctly paired with the verb falar, with varying meanings.
In the case of falar a (talk to) and falar com (talk with), falar com is indeed more commonly heard, but this also has to do with the base meaning of each one - we are more likely to talk with people (mutual exchange) than to them (unilaterally, if interpreted literally) I would say that there’s a bit less interchangeability between falar a and falar com in Portuguese than there is between talking to and talking with in English.