Crossfit is dubious in my experience. There's some awful form demonstrated on many of the lifts and very little training of how to do things properly, essentially a load of injuries waiting to happen.
Many people are in great shape from doing it, but I bet they were already in great shape.
It's fashionable for some mad reason, but then if that kind of training appeals then go for it.
I think you'd get more from a decent proven weightlifting routine with a mixture of mountainbiking and "fun" sports.
I mentioned him already in this thread, but Dan John, has tried it all and is very entertaining
http://danjohn.net/