2 in mine. My Varisia campaign has 5 PCs - 1 elf 1 goliath 1 dragonborn & 2 human. My Primeval Thule game has had a couple dozen PCs, the goliath is the only non-human in the 'regular cast'. Occasional & one-off PCs have included 2 elves.
I think people who are aware of goliaths play them a fair bit.
The Goliath work particularly well in my Runelords/Varisia campaign as uber-Shoanti; the adventures involve a lot of high mountains, and Goliath culture fits in extremely well there. They're less suited to a typical Forgotten Realms type fantasy setting - albeit dragonborn, or tiefling PCs with giant horns, aren't that well suited to trad fantasy either.