Even the latest Tesla only reaches ~1.5G - not even that. G-LOC won't happen until 5 or 6, so I think we're a way off yet!
Roller coasters tend to hit a good amount of gs, but if you pass out you'll be fine since you're not driving. One wonders if a Tesla detects its pilot unconscious can it bring itself to a full emergency stop. Automatically contact emts and then automatically distribute snacks to the arriving EMTs