Mexico City - Job Market
Since labor in Mexico is very cheap and job offers are few, the line of applicants is very large for any opening and most of the candidates have high university degrees and speak at least English.
One place where non-native Spanish speakers can get a toe-hold, is in language teaching. The foreign languages most in demand at the moment are English and German. French is also quite popular. If you are a native Spanish speaker, then there will be lots of expat spouses to teach!
When applying for a job, it is the "thickness" of the application that is most important. Do not just send your CV and a cover letter. Send a copy of every single certificate you've ever got since you graduated high school, including your high school diploma.
For most jobs you will require very good Spanish and most importantly a work permit.