They offer prospective students to stay at a current grad student accommodation, but I don't know, I'm thinking that depending on who you get this could be incredibly awkward ... did any of the older students used that option ? Would you recommend it ?
The two schools I visited last year that had programs like this were Berkeley and Stanford. I suppose it could be pretty awkward but as long as you're a reasonable human being I wouldn't expect it to be a problem. At Stanford I stayed on a couch in an apartment which had four or five physics PhD students. At Berkeley I stayed in a grad student's room at a co-op, which had the potential for awkwardness (theoretically it was the clothing optional co-op but there weren't any naked people running around -- just plenty of weed and granola).
Neither of them were in fact awkward, other than the normal awkwardness of meeting lots of new people really quickly, and I felt that both of them offered interesting slices of life at their respective schools that I didn't get when I visited, say, Santa Barbara. Consider that if you end up staying in a hotel, you're going to be sharing a room with another prospective student anyway, at least if the school is paying for it. If the option to stay with a current grad is there, I'd recommend you take it.