I was accepted to UIUC and UW-Madison, so I notified all other schools that I won't be going there as soon as I got acceptance from these two. I haven't contacted any professors from UC Davis, but you should probably do so if you're interested in the result.
I also haven't heard anything from UC Davis yet (I applied for PhD). Not that I care too much about that though as I've been accepted to a couple of better schools, but it still surprises me that it takes them too long. It's not very smart of them if they want to attract potential students.