Once in shape, he should handle 65 lbs or so. It depends some on the distance and terrain, but he is a decent sized goat. As far as tacos are concerned... Goats are a very under rated meat. We had one tear a ligament last year in the pasture and butchered him. Pretty good eating.
I've got another that weighs in about 165 lbs and he and this one will pack a boned deer and my gear out fine. I've a couple of more younger ones that should be good in a year or two as well.