DS was exactly the same (23/24 months). What we did was progress to putting pants on him and then watching him. When he went to sit on his potty we just said "Pants down!" and pulled them down for him. After a few goes he would then say "pants down" and wait for us to help him do it. We've now started asking him to help pull them up and down.
I have let DS 2.1 go nuddy the past 2 afternoons just to see if he would take to the potty really. He has done really well and has done ALL his wee wees on the potty (proud mummy alert) :-) But he never actually tells me he wants to wee he just goes and sits down and gets on with it. So I'm a bit confused, if I was to put some little undies on him how will I know if he needs to use the potty???