Megilla on 15th of Adar has nothing to do with Eretz Yisroel.
It has to do with walled cities (at the time of the Story of Purim or the times of Yehoshua bin Nun [machlokes]) at the sorrounding area. Most areas in EY have Purim on 14 w/ the exception of Yerushalayim Yafo and even in the times of Gemara Tiveria was a machlokes.
As the exact location of Efrat, I don’t know, but they probably have Purim on 14 Adar.