Bougainvillea itself is reportedly mildly toxic to people, though the flowers are safe. My tortoises have access to it, but hardly pay attention to it. I have eaten it myself before (curious why they weren't interested) and it tastes a little soapy...not very delicious. Also it has some killer thorns on it! I have never had a tortoise injured by one and know they have a lot of armor but those things could definitely do some damage to soft tissue or an eye.
Also I am not positive on the yellow flowers but it looks an awful lot like Allamanda (the flower more so that the bush) to me, and if it is that's part of the oleander family and a definite do-not-feed so I would be cautious until you get a definite id on it.
A vet once told me that any flower with a leather like feel ie frangipani should never be given to animals. The yellow one looks leathery. Also if it is from the oleander family I wouldn't have it close to young children either since it's very poisonous. My greek torts love hibiscus flower and leaves. Grows easily in warm climate in garden or pot