OK, I couldn't find the answer to this either, but I just found this:
http://community.simtropolis.com/topic/59596-mac-os-x-mod-plachement/
Looks like if you secondary click the app itself and select "show package contents," then /contents/resources/simcitydata
I even looked in the app myself, but didn't see the data folder in the resources folder. Going to test it out now!