Answer
a. Yes, you warm the balloon.
b. The temperature of the air expanding from the balloon becomes lower, i.e., it cools down.
Work Step by Step
When air in the balloon is compressed, work is done on it. Its internal energy will increase, along with its temperature. The air, and the balloon, become warmer.
On the other hand, when you release air from the balloon, the expanding air performs work on its surroundings. The air's internal energy decreases, along with its temperature.
Both of the above are adiabatic processes, as described on page 341.
