It's time to renew your plates.
You can do it online using this site: http://www.tenencias.gob.mx
I have used it before, and it is really easy. You prepay, take the printout of payment, your registration, and your plates to the "DMV".
YSkip the window line, and go directly to the lower desk and present your documents.
The new plates will NOT be available until sometime in March. So, another trip is necessary to pick them up.
As long as you have current registration, no one should be concerned with running without plates.