You're right, when using a Leonardo the baud rate makes no difference: either in Serial.begin or in the Serial Monitor. There are a couple recent Yun Shield discussions going: one using a Leonardo, and one using a Mega2560 - and I couldn't immediately remember which one you were using.
stgeorge:
Interestingly though, when the Arduino IDE's serial monitor pops up, the default rate is 300 baud ?!
I'm guessing you changed it at some point in the past and forgot about it. When the Serial Monitor opens, it remembers the settings you had used last time.
One thing to be aware of with the Leonardo is that the USB serial port is created by the sketch software itself. Every time you load new code, or reset the Leonardo, the serial port goes away briefly, and then appears again. I found that I generally have to close and reopen the serial terminal emulator to see any output every time that the sketch restarts. That may be what is happening here: try starting the sketch, and THEN open the Serial Monitor and see if that makes any difference. That's why so many example sketches have this:
while (!Serial)
;
When converted to a boolean, Serial will initially be false until a USB serial connection is made. Since the while loop checking this does nothing (has just an empty semicolon) the sketch will wait until a connection is made. This is because on these systems, the connection cannot be established until after the sketch starts and Serial.begin() has been called. This construct is used when setup() wants to print out some initial information that you want to capture on the Serial Monitor. By waiting for a connection, those initial messages aren't printed out before there is a chance to make a connection.
That's not really a concern in your case, since there are no other messages printed at startup. The only thing you're looking for is any messages printed when you press the button.
stgeorge:
Not sure exactly what you mean by "code tags" ? I guess I'm slow, but don't follow that one...