Disclaimer: not including any commercial providers here, as they are usually more expensive. With today’s online learning resources (raywenderlich.com tutorial, stackoverflow to say a few), it’s fairly straightforward for an experienced developer to pick up Objective C and UIKit, etc. I think the value of classes is mostly from interaction with instructors, and do some real life projects.
Last but not least, the St. Louis iOS group led by Brian Coyner. The format is different from the training class, but it’s a good place to hang out with fellow iOS developers in the area. For that matter, there is a mobile dev group with an emphasis on Android (led by Heath Borders) as well.