Start a new group.
Add a text object and type 'a'.
Select the layer and Duplicate: change the letter to 'b'
continue for each letter you want to "spray".
Select the Group and add a New Group (for the emitter)
Pick one text object (one character) and turn it into an emitter.
Drag the Emitter up to the empty group.
Set the cell controls you think you want (Birth rate, speed, spin, stuff like that)
Select ALL the *other* text layers and drag them ONTO the emitter -- they'll all be added to the emitter and each will be randomly selected when the emitter fires.
Go back to the first "cell" (letter) you added and whose "controls" you edited. Shift select the parameters you changed and drag them onto each of the other letter layers in the layers list (that will copy the parameter values to each one without having to go into each one individually and make changes.)
(I only did letters a - e:)
Hope that's what you're looking for.