Have NICU as your first choice, and then, if I were you, I'd stick to one of the following (in this order): Well Baby nursery, Mother/Baby, Pediatrics, PICU. Try to stay close to the babies if at all possible- Well Baby nursery is sort of like med/surg for babies. You'll learn all about what a normal infant looks like, routines for the unit, and we do a lot of similar things (like starting IV's, giving antibiotics, feeding, assessments, transfers, teaching to parents, etc.). Mother/Baby is not as baby-intensive, but you'll still get an opportunity to be around the babies and help to teach the moms the same things you'll be teaching parents in the NICU (though on a less-narrow level- stuff like discharge teaching, normal newborn care, breastfeeding, etc.). Pediatrics is next on my list, but you won't be working with just babies; Peds is to age 17 or so, so you'll likely be working with a wide variety of ages. Still helpful (all experience is helpful!) but not as applicable TECHNICALLY. I recommend PICU last only because I don't think as a student you should be in such a fast-paced environment...there is PLENTY of time for you to go rushing head-first into intensive care once you've graduated.
Good luck! Let us know what you get!