contract question

I'm about to sign my first contract, but i'm not sure about the per diem part.
The actual pay rate is $11.00/hour with a per diem rate of $115.43/day. I'll be working 3 12's, but the hospital is only an hour and 1/2 away, so i will only be staying overnite one or two days. So will I be taxed on the rest of the per diem rate, minus the actual expenses of the 3 days i'll be working? I tried to call my account, but only got an answering machine.
Thanks