The school building is being completely torn down, and students are going to Radnor this fall. I *think* it's a two-year project.
If your child is going into 2nd grade, he or she will need to test in to the immersion program, meaning some previous Spanish language ability is needed. This is also providing that a spot is open in 2nd grade, which there very well may not be. The lottery is for K and open spots in 1st. Not sure if there is a lottery/waiting list for kids that test in later on.
The RCF Spanish immersion and the English Academy (non-immersion) are both well-respected on this board. Some earlier threads discussed a division between the students/parents from the two programs, but my understanding is that that is not really the case anymore.
Also worth noting, there are two ES schools with "Rock Creek" in them--the other is Rock Creek Valley, which does not have immersion. Just so you don't get confused!