When should I tell them?

I have 2 best friends I have known since middle school. I go to college in California, they go to the same school in Arizona; we are all from New York. At their school, a year or 2 ago they participated in the refounding and rechartering of an Alpha Beta Iota fraternity chapter that been formerly defunct, which made them new founding fathers. Every once in a while they would tell me to pledge/join the chapter of their Alpha Beta Iota fraternity at my school, but it never really crossed my mind because I was really busy my first 2 years of school. Now, as a junior, I pledged a fraternity (Alpha Beta Delta) this semester, seeking a new experience and outlet on the campus. However, the fraternity chapter I pledged at my school Alpha Beta Delta is not the same fraternity my friends refounded at their school. I had considered the Alpha Beta Iota chapter at my school but I didn't find the guys in it to be that welcoming or as genuine as the guys in the Alpha Beta Delta fraternity at my school. I'd like to tell my friends that I pledged a fraternity, but not sure what their reaction will be that it isn't the one they are part of. Should I just tell them now? If they are truly my friends then they won't turn their backs on me, I would think.