Yep, even the top young players spend a couple of years in the Minors.
(There's the odd exception, like one of my favourite players, John Olerud)
There's a few old vets playing in Triple-A (the highest level of the Minors), stashed there by their MLB team as insurance in case of injury to someone on the Major League squad.
However, most Minor Leaguers are trying to work their way up the pyramid.
The Brooklyn and SI games I go to are at the second lowest level. The players are normally in their late teens or very early 20s
As well as the two Minor Lesgue games I'm going to in NYC, I'll also be attending some others the following week when I meet up with some friends to travel thro Pennsylvania
http://www.sportstravelandtours.com/WebPackage.asp?RowId=58150000