I can't tell you much about the fz 50.
But I can tell you the S2 and S3 are really nice cameras to work with. Many options that can be adjusted, lots of great features, you can step the flash up and down on the S2 (not sure about the 3, but most likely the same) They have the IS (image stabilization) which is wonderful for some hand held shots. Tons of features to learn with, they pack a lot of bang for the buck! Personally I have learned so much by using the S2, when I step up to an SLR (in the way future) I don't think I'll feel to lost. Hope that helps you out a little.
See if you can go handle each of them in a shop, I personally like a little bit bigger camera. I'm 6' tall, so having small things to work with can be an issue.
Okay that's my 2 cents. Best of luck, do let us know what you choose!