You can use puts/prints in the EWL hello world project created for Kinetis devices in the UART environment. You will need to make the following changes to build settings using EWL with the Kinetis gcc compiler and build tools. To perform the steps below, first create a project using the new project wizard (File > New > Bareboard Project > Kinetis L Series > KL2x Family > KL25Z ) and select the derivative MKL25Z128. Next, select UART as I/O Support.
The steps below are for the ConsoleIO support for TWR-KL25Z128 + TRW-SER boards but the same steps can be applied for the other boards supported.