Savil agrees with him that they're fascinating! They do have minds, for a certain definition of 'mind'; none of them are as intelligent as people, it's hard to compare because they're quite different but they seem to vary between, oh, 'snail' and 'unusually clever dog'. The difference is that Mindspeech, or something akin to it, is their native communication. "Imagine a snail that could talk to you!" she says at one point.
Each plane (earth, air, fire, water) has its own set of elementals, coming in several types or 'species' that vary in intelligence and cooperativeness with summonings. (Savil isn't sure if they mate and reproduce like ordinary species in the material plane; she doesn't know how to visit their home planes, though there are rumours that some schools of magic teach how mages can project their minds there, and it's not the kind of question they understand and answer). Savil isn't sure if individual elementals of the same type vary; she generally can't tell them apart.
Elementals of different planes vary quite a lot; air elementals have an affinity for minds, which makes them easier to study and interact with, thus Deedre's successes. Water elementals seem to have an odd, sideways, but surprisingly acute perception of weather patterns in the material plane. Savil had kind of hoped she could incorporate them into weather-magic somehow, but ended up stuck on communicating to them what she wanted.