It all depends on the closing costs and new interest rate. A no-cost refi with a lower rate is a no-brainer, assuming you don't go out and blow your new-found savings on stupid stuff.
Take this equation:
( Refi closing costs) / (old interest payment - new interest payment) = number of months to payback, assuming a fairly short-term situation like yours. If the time-to-payback is more than the time you expect to be in the house, then it's not worth it. If it's shorter, then it's probably worth pursuing.