I would get into a high acuity ICU full time for at least a year.. traveling and per diem show flexibility, but you don't get the training that you would from being regular staff in an ICU. I traveled for a year and a half, and rarely got to care for the vented patients on multiple pressors. I know that most schools require at least one year full time ICU experience, so I don't think that per diem would count towards that. Good luck!