Urgent: need help: re-finance for rent or sell the house

I rented my house 2yrs ago and the tenant will move out Aug/2011. Current mortgage is 7yrs arm 30yrs loan with rate of 5.25%, will expire in Oct 2012. Should I re-finance now or just sale the house?
If re-finance now, 15yrs fixed rate is 4.375~4.5%, monthly loan +tax+insurance+other expenses is about $$2775, rental income is only about 76% of the expense, worth or not? Should I just consider the interest of the loan as rental expense not the principle when I calculate my net cash flow?
If sale, I think I will loss at least 12% of the house value.
I need a decision quickly, as current rate is very low. Really appreciate anyone’s advice and help.