University Medical Center is Tucson's "teaching hospital." You will encounter student of all kinds there (nursing, medical RT, etc.). I work there as a PCT and enjoy it. Northwest Hospital will take anyone. I've heard good and bad things about TMC - it depends on which unit you work on. St. Joe's and St. Mary's are both good hospitals as well, and then there is the VA and Tucson Heart Hospital. My sister is a traveler who has worked at Northwest Hospital, TMC, and St. Mary's. She will not go back to TMC because of the way she was treated by the workers there. She is very disappointed with the attitude of the management at Northwest. She has renewed her contract 3 times with St. Mary's and just signed on as a seasonal worker there.
As a student nurse I have worked at UMC (loved it), Tucson Heart Hospital (small and very nice), El Dorado (hated it), and St. Mary's (accepted a new grad position there - great benefits). This last semester I will have clinicals at TMC so will find out for myself. Hope this helps. (Please keep in mind that these were the experiences of just two people and may not reflect the experiences of others.)