from what i've heard, the tree should be just as cold hearty as M. glazioviana, or even stronger....(m. glazioviana can withstand about 26-28F without dying, but sometimes will have severe damage depending on size of plant, and duration of cold.)
i've also heard that M. guaquiea is generally more precocious than M. glazioviana fruiting from seed in about 3yrs. (glazioviana takes about 3-5, in my area)
of course guaquiea has smaller seeds and more edible pulp!
not sure about pH sensitivity, but I'm assuming it's much like M. glazioviana.
I should have some seeds left....just send me an email to make a reservation....and I will let you know asap!