fruits of physalis are a special interest of mine, so it's disambiguation time!
there are are least two very different species of Physalis being discussed in this
thread. true cape gooseberry, P. peruviana (aka goldenberry or incaberry), is a
perennial (though not in much of north america), native to south america. the fruit are larger and sourer (i usually find the taste akin to 'tang' - citrussy and slightly more sour than sweet). this plant was taken from south america to many places - it seems to be the fact that it was grown in south africa that's given the name 'cape' gooseberry (while not being either a gooseberry or from the cape). 'New Hanover' and other varieties more frequently called 'ground cherries' are mostly P. pruinosa. they're all annual and make a smaller sweeter fruit. there also several north american native perennial species (in my area, most notably P. longifolia and P. heterophylla), the latter of which makes fairly large greenish fruit with a purple blush and has a very tropical-ish flavor, probably my favorite, flavorwise. not particularly productive, though. most species (though not P. longifolia) will drop the fruit when it's dead ripe. picking off the plant can frequently yield sourer fruit.
unfortunately, where i am i have a pest that's particularly damaging to Physalis fruits. it's a little slightly fuzzy black worm (insect larva - not positive whether it's a beetle or a moth) that climbs the plants and burrows into unripe fruit. they do it to tomatillos some, too (another Physalis fruit!). this has brought my experimental interspecies breeding work (trying to get a more productive perennial physalis) to a stop for a bit. hoping to pick it back up this next year, but it'll probably have to be in pots on a table.