So a quick dip into C++ can get you started, only if you already know C.
Well one fallout of the Arduino's popularity, for good or bad, is that there is and will continue to be thousands and thousands of new people learning to program their Arduino boards and not knowing what parts they are learning are C and what parts are C++. Not sure if that is good or bad, just different from the more traditional learning transition I would think? None of the Arduino documentation seems to deal with this, and it doesn't seem to matter much to the goal of learning to program ones Arduino.
Lefty