You'll spend the most time with the interns/residents and other students on your team. How much you see your attending will vary on the rotation... in Surgery, we frequently only saw our attending when we were in the OR, or when the residents were giving quick updates to the floor patients. We rounded with the residents. On ophthalmology, I virtually never saw the attending. On medicine, we rounded with the attendings, and then my attendings would give some sort of afternoon lecture. On inpatient peds, I pretty much only saw my attendings for rounds or when I had to present a patient that came in during the afternoon. On OB, I pretty much only saw the attending when there was a C-section, or briefly during vaginal births.
When I was in clinic, I worked primarily with attendings (except surgery clinic, then I worked with the NPs more), either because the residents had their own patients to see and present, or because there weren't any residents in the clinic.
The only time I really worked with MS4s was when I was on medicine (I was on in July) and Peds (September), when they were either doing away rotations on our service, or were doing their sub-I. Otherwise, I only saw them in passing in the halls.
The MS3s not on my team--if they were on the same service as me, I'd see them at lectures, but otherwise, it was really intermittent. I saw some of the peds people more when I was on OB, and saw a number of students when I was on psych consults, but beyond that, I didn't really see MS3s not on rotations with me.