Without putting a dampener on things, I think you might really struggle getting a 'temporary' ATCA position. Presuming your a self funder, if I were you I would complete the ADI course as well before trying (and I stress trying) to get a position as an ATCA.
Don't presume that if you have a student license units will be falling over one another to employ you as an ATCA either, because there is a lot of competition in the same boat as you out there. I would hope that whichever college it is that's training you has explained all of this already.
Don't take this as negative feedback, just some honest opinion based on personal experience from when I started out.