...and I agree with you. "Talking" is more common because I have heard that "to speak" is used only in formal situations and when one states what language(s) he/she speaks ("I speak X" (insert language(s) here)). So, unless one is at a job interview or talking to his/her boss, the verb "to talk" will almost always be used.
I believe that is true for all English variations (British English, American English, and so on).
As a native English speaker, I think in general you're on the right track, but not quite accurate. One would definitely say "I speak X language" (rather than use "talk" - which would clearly sound wrong unless you're a Cockney) but I wouldn't say that in other cases "to speak" is ONLY used in formal situations - that's a little too prescriptive and not necessarily true. This is a rather "grey" area but in general I would say that "to talk" is more common and can be used in both formal and informal conversations. However, I suppose "to speak" may arguably sound a little more "educated" in certain situations.