I did Chicago to Chiapas (and then Central and South America) almost a year ago--great trip, and one which is still on-going. Mexico has so much to offer. Unless you have unlimited time it's hard to decide what to see and where to go. Right now your biggest decision, I think, is where to drop into Mexico. Do you go all the way west and go down the Baja and then take the ferry across from La Paz, or do you drop in through Douglas, Arizona and ride through the Copper Canyon, which should not be missed?
I'm sure you have already done so, but check out the many excellent ride reports here on ADV on Mexico. Here are a few I would recommend from tricepilot
Treasures of the Sierra Madre
Copper Canyon & Bitopilas
On Mexican Time