Kirstey
A PA28 does have an AOA indicator. It's called the AI (Attitude Indicator), but the PPL syllabus minimises reference to it apart from the instrument appreciation, because (as you infer correctly) PPL students are trained to fly airspeeds because its a less tricky concept at that stage and getting the prospective pilot to look outside rather than fixate on the panel is important at this stage.
As to stalling a PA28, this is very easy; what is not so easy is obtaining a "g" break due to the aerodynamics - it tends to "mush down" stalled, but benign.
If you are interested in stalling, you could do a search - I think that John Farley (a very experienced test pilot) made a super posting explaining the difference between being stalled and a g break.
The only caveat on the PA28 that I know of is that the taper wing versions, when loaded to the rear of the W&B envelope can give you the mother of all wing drops which comes as a nasty surprise when they don't usually break at all.
I understand what Stik and the other guys are saying - I'm not knocking QDM, but you're probably not going to want to fly a Cub in IMC and if you did, you could fly it on airspeed, power and turn co-ordinator. Having said that, we don't know why QDM needs the device, so there may be good reasons, although claibration will be interesting.