I work at a vet clinic, and one of my coworkers rescues St. Bernards. She has had many through out her life. She has three right now, and one bichon. These three HUGE dogs are SOO sweet. She has three kids of her own that grew up with saints, and all of her dogs were wonderful with them. Now her kids are grown up and her 18 month old grand daughter loves these dogs. She can do whateve she wants, and all of these dogs are So gentle with her. And she rescued all of these dogs as adults. They are all wonderful.
The only thing is that you have to have room for them. They are not hyper dogs, just BIG dogs, and they take up a lot of room. And they are also expensive. Their food costs and vet bills are out rageous. My friend does not make a lot of money, but she devotes a lot of it to the dogs, and does just fine. Good Luck with your search. Do a little more research on the breed so you know they are right for you. But they really are very nice dogs.
Oh, one more thing...They DROOL! My friend carries around a slobber rag with her whenever she has the dogs. They can be very slobbery.