Welcome!

I'm sure you'll find from other replies that this is a very personal choice. Some people only tell a few close friends/family, others choose to disclose everything to everyone, and everything in between.
Me personally. At first, I only told my parents. We're very close, and they have always been a huge help and support for me. A few months later I talked with a couple of friends about it. These are people I trust completely. I felt they deserved to know, given all they had to put up with, and they are also a source of support. It's also helpful to have people around me who notice when things are going south.
As for the work environment, one of these friends works with me. I hadn't planned on telling anyone else, but those plans went down the drain...

Eventually, it got so bad I had to speak with my boss. I'm very fortunate, he was very understanding, not at all judgmental. I still don't like it, but it's done and it was my own responsibility, so...
My advice would be to think long and hard about who you really trust. Don't just decide things in the spur of the moment. Consider everything, make a decision, think some more, and then do it. Still, I do think it's good to have other people know about our diagnosis. It's a source of support, they can help if need be, and it allows us to share some of the burden. So long as you trust the right people.
Again, this is a very personal choice, so take what you get here and really think about it.