I recently joined the Navy DEP and I chose the EM rating can I change to IT?

I recently joined the DEP and I'm shipping out on Nov. 25 and I chose the EM (electricians mate) rating. I wanted the IT rating and I did qualify for it but since my mom is a permanent resident I couldn't get it because of the security clearances. I was wondering if I could change my rate before a ship out and if I can't, is the EM rating bad?