There are currently six regulars at the ALDC on the show.
If you want all dancers ever, here's a start:
That isn't all of them. I can think of a number from the ALDC that were in full dances on the show that aren't listed in those. (Brooke K. in a duet with Mackenzie, three seniors in this dance.)
And there are unlisted dancers in featured dances from places like the Murrieta Dance Project, Studio Bleu, "Studio Larkin," etc.
There'd be lots and lots and lots more, if counting people in background shots (like you can see briefly dancing at a competition, training at the ALDC, or just walking around.)
And some of the adults seen choreographing still seriously dance, too.