Yeah, I did epi. We didn't officially have public health or epi depts, but we had a epidemiologist on the faculty in the nutrition dept. She was good because she taught me basic statistics to run my analysis, and also taught me how to use SAS (which is very helpful). Also, she had access to lots of free data (NHANES, in my case).
But, yeah - basic research probably helps for the application / uniqueness factor, but might not be as helpful in the "prepping you for classes" area. Although - some options might be pretty close to public health (microbiology if you are interested in infectious disease epi, toxicology or organic chem if you like environmental health, human genetics, etc). Or even social science research if you want to learn some statistics.