make sure that you add coolant though ASAP. I see that you live in Arizona... you will need coolant for sure down there, water alone will not transfer heat all that well compared to the coolant, plus the coolant rises the boiling point of the water.
you may need to drain some water to add the proper amount of coolant, so go and buy a little coolant tester from your local auto parts store. ( usually around $10 ) test your coolant and add more as needed.
Remember that adding straight water is merely a band-aid to get you home, and you don't really want to be using that alone for any long period of time.
one last thing. do you have any idea where the old coolant went to? might want to dig into that and find out where it went.