On my return to Guatemala this year I'm considering a trip through the Copper Canyon. This would be a start date of about April 2 or so from ElPaso area. I found that this is a decent time as it is before the heat of summer so rivers are not too bad. If you are interested let me know via posting here or PM.
I will not be risking it solo due to river crossings etc. so without a partner truck or two this will not happen and we'll simply bypass Copper Canyon for this year.