I will be in Yerushalayim for Succos IY"H and want to know what I do about putting on tefillin on Chol Hamoed. I daven Ashkenaz and put on Tefillin in the States. Are there any special Halachas I should know/follow when in Yerushalayim?

You should put on Teffilin Betzina'a - in a place where you cannot be seen. Rabbi Nir Sinai