My husband and I are in the process of pricing out a floor plan with a local ICF installer. We are interested in doing an all ICF home. Our new home would include a basement with two levels above ground. I'm a little worried about cell phone signal. Does anyone with all ICF homes have issues with cell reception?

For the most part, you shouldn't have serious issues unless, possibly, you're going with something like Helix.
If you run into an issue, a bi-directional cell phone booster isn't terribly expensive.

While there is significant insertion losses in the 0.5-2Ghz band with concrete, if the house has windows you won't experience much attenuation from a practical point of view. People can still use their cell phones in large concrete walled commercial & industrial buildings with few windows, after all. see: http://ece-research.unm.edu/summa/notes/In/IN624.pdf

Regarding Helix, I have it in my own home and my signal is hardly altered inside versus outside. Out of over 100 ICF homes built, only 2 have trouble. I cannot discover any common thread between them. One is Durisol, the other Nudura. One is rural, the other city. One has Kensington windows with heat shield, the other triple pane Loewen....

Question, is the rebar structure grounded or ungrounded?