Sounds like you've already lined up a summer project at your home institution in immunology, so going to a place with an academic ENT department (with residents) isn't going to happen. If you want non bench ENT projects, many students/residents would pick some retrospective chart review. It's easy to get tons of data in a short amount of time - and many journals in our field publish a lot of this kind of research. If you are committed to staying at your own med school, it would be very difficult to get involved with this type of project at another institution. Let's face it - the med students role is usually abstracting the data from the patients' charts and then looking for trends with their advisers (then writing, of course). If you approach your own institutions ENT attendings - I'd look for someone who has a niche practice and see tons of patients with specific types of pathology and if they have any clinical outcomes questions that may be answered with the charts you would have access to at your home institution.
If you do decide to approach another institution for a project/mentor/PI, one would go to the attending directly or via the coordinator of research. Residents (at least where I am at) would be of little assistance in coordinating a new project, and may want to go first in authorship if they're involved.
We occasionally do get Sub-I's that ask for a clinical project while they're on service, and a few have had manuscripts accepted from their time with us.
Case reports are nice but the ones that have come from my institution in recent years usually are written up by the resident who took care of/operated on the patient.