Ok, it's getting clearer.
If there is only IMSS hospital in town, people join IMSS. If - Seguro, then Seguro.
Or they join both palns - and then pay both annual premiums unless they are so poor that are exempt from paying one or both premiums.
Then they have access to both IMSS and Seguro - which still might not be good enough, and then gringo goes North for Medicare and Mexican has to pay out of pocket for private, or die.
Canadian living more than 6-7 months will either use private coverage, and then pay $$$ for whatever is not covered, or again die while trying to return North and waiting 3 months in Canada before he becomes eligible for provincial plan that was discontinued during his absence.
Mex - can you confirm that full IMSS including free meds is only available to membership through employer? Because this is what I hear, and this sounds cruel if there is only IMSS hospital in town. Any local - including gringo with status - should be eligible then.