I just brewed the Northern Brewer "El Modelo de Mayo" this past Saturday (5/4).
I've got it fermenting at 50 degrees and is doing really well. Nice Krausen.
One thing I've noticed in the NB Instructions -- they don't mention a diacetyl rest.
Once it is done fermenting, take the temperature up to room temp (68-70) for a few days (this allows the yeast to reabsorb the diacetyl), rack into secondary, then proceed with the gradual temperature lowering (lagering).