I also live in Tucson and completed an externship at The University of Arizona Medical Center- University Campus last summer. I would absolutely recommend this hospital! They have a great nurse to patient ratio, are magnet status, and offer an 8 week paid summer externship. They typically hire externs in general pediatrics, as well as the PICU, NICU and peds hematology/oncology. The only requirement is that you will have completed 3 semesters of nursing school
by the time the externship starts. The applications generally open in March or April, but I would recommend calling nurse recruitment to get a better idea of the exact dates. They updated the website and I couldn't find externship info, so I would just call the operator at 520-694-0111 and ask for nurse recruitment. They are usually great about getting back to you.
I think it is so smart that you are thinking of looking for a summer position...it is extremely beneficial, and you will feel like 4th semester is a breeze after your externship! Also, many of my classmates (myself included) were offered RN positions on the floor where they were externs. Please let me know if you have any other questions!