In case anyone is thinking of an MHD with a MEX turnaround, be warned that some flights into and out of MEX are being cancelled due to nearby volcanic activity. See http://www.flyertalk.com/forum/Forum...ML/001414.html for more details. (Hey BlondeBomber! Still going?

Guadalajara (GDL) is probably a good alternative, as from most Canadian cities it is as low or lower fare than MEX, yet still a major enough centre to have several non-stops to/from places like ORD and SFO. Same day turnaround might be a little more tricky.