I'm in San Diego and would say there is trustworthy dealers, but also some that are not. But any engine work where you need an "engine mechanic" is usually an intricate job and a dealer is the first place I'd go for something engine related I didn't feel like tackling myself - within warranty or not.
What Overlander said, could you elaborate? The kind of issue you're having could attribute to the quality of work your Jeep may need.