Don't use tap water in your radiator unless it was an emergency. And if you do, as soon as you can you need to drain and flush the radiator with distilled water.
Regular water will cause build up and mineral deposits, and believe me, you don't want that.
Around here, if you do track days they want you to drain your coolant and use dionized/distalled water. So if you wreck and your fluid spills, it doesn't leave slippery residue on the track. Most people then ride home with the water and then drain and refill once they get home.
As far as coolant is concerned, use a coolant formulated for aluminum engines. You don't want to use regular anti-freeze stuff like Prestone, no no no no no.
I use Coolanol by Maxima Racing Lubricants. I don't know if it's the best stuff out there, but it seems to work fine for me, and it gets into the 100° F range here in the summer. This stuff is a antifreeze and deionized water blend, so you don't have to delute or mix it at all. Pretty convenient.
Hope that helps.
"We are what we repeatedly do. Excellence, then, is not an act, but habit"