I am very familiar with the Claremont Colleges (Pomona, Claremont McKenna, Pitzer, Scripps, Harvey Mudd), but only have a few friends of friends that I know who went to grad school at CGU. Claremont McKenna has a strong foundation in politics and government, so I am going to assume that the graduate institute has similar teaching philosophies if they are related. Most of them were interested in economics/politics/government.
As far as the ranking of its MPH/PhD programs, I'm not sure where CGU stands, but I know that it would be a very small program, seeing as the undergrad colleges are fairly small. I have a few friends that did their Post-Bac at Scripps College, and really thrived because of the professor to student ratio.
CGUs PhD program is newer, but the faculty are well versed in their fields. If you look at their CVs most of them are from the preventive medicine department at USC. In my opinion, it really is going to be based on the match of the faculty and their research. You should get some great mentorship there, but more than likely you'll need to be a match for the current faculty and their research funding streams.
If anything, find a few faculty you are interested and start an e-mail conversation.