Guinea Pigs can take -15C, maybe less. Just can't take SUDDEN changes in temperature. So no wonder they suspicious.
We had them living outdoors for about 12 years. They live "wild" all the way from Tropical Amazonian swamps to snow line of Andes in Peru. Very versitile. But bringing them into Central Heating from Cold Outdoors can kill them. Even though they can cope with 30C summer.
People keeping pets should research them better. Could avoid visits from "pigs" :-)
Lawn around our bird table regulary spawns Opium Poppy (common flower bed plant) and Hemp from the bird seed. Cannabis is kind of hemp. It's grown also outdoors as a clothing fibre. I don't think much used for rope anymore.
Industrial Hemp http://en.wikipedia.org/wiki/Hemp
"common garden poppy" http://en.wikipedia.org/wiki/Opium_poppy
I'm sure there are interesting mushrooms in the nearby woods. The "lawyer's wig" that grows in our own garden is lovely fried. (Autumn Fruit)
We have "fake castor oil" plant (Fatsia japonica) not this one http://en.wikipedia.org/wiki/Castor_oil_plant which makes Ricin, but we do get Spurge growing as a weed.
Not just South Americans, but Italians eat Guinea Pigs. I don't think it's for any "mind bending". Supposed to be a bit like rabbit.