Delete your range selector and replace it wtih an expression selector. Put this code in your expression selector's "amount" property. You can edit the delay, frequenccy, amplitude and decay to time it and change the other characteristics of the bounce. I'd pickwhip those values to slider controls in your effects panel so you can keyframe them and edit more easily in general. You can even select all your sliders and the new text animator in your layers and save them as a new effect so you don't need to set it up again in the future.
delay = .1;
myDelay = delay*textIndex;
t = (time - inPoint) - myDelay;
amplitude = 150;
decay = 8.0;
s = amplitude*Math.cos(freq*t*2*Math.PI)/Math.exp(decay*t);