If you see or are approached by a hungry tortoise, do not touch, and most importantly, do not pick them up to move them. Doing so will scare them and often cause them to pee which can dehydrate them and possibly kill them if they can't find enough fluids to safely hibernate.
Taking them home with you is especially dangerous for the tortoises as they require special care, diets, climate conditions and expert veterinarians. They can also pick up parasites, worms and other diseases detrimental to their health while also spreading diseases to others in their new environment. I can tell you from personal experience that it is awful treating a tortoise with pneumonia and other medical conditions caused by a change of address. A tortoise left alone in his or her natural habitat can live over 100 years. Unfortunately, thanks to people, their main predator, the tortoise population has been decimated to such an extent that they are legally a protected species.
If that doesn't convince you - they bite!
Finally, California Department of Fish and Wildlife (formerly, Fish and Game) has issued a similar warning about Western Pond Turtles -"if you care, leave them there". Though water turtles, they will come on land to bask or lay eggs and do not need rescuing.
Please-don't take anything from the wild except a picture!