What Should You Expect?
When you watch the experiment you should see the water turning towards the balloon and here's why. When the negatively charged balloon comes near the water, it repels the electrons in the water, so that the side of the water nearest the balloon then has a positive charge. The attraction between this positive charge and the negative charged balloon results in a net force* on the water, bending the stream of water.
* net force: overall force acting apon an object.