Over temp, puking water, elec fan etc

[walker]

Well the heat is here in Phoenix once again. Tonight after driving from town to the store near my house I parked the truck and went in the store for about ten minutes. When I came back the temp guage was way up, and the truck had puked coolant. I know why it does it but would like to know how to prevent it, as it runs poorly and doesn't like to start easily in this condition. I am a little confused too because this does not happen every time, just every once in a while, and I cannot figure out why it does it sometimes and not others.
I have also been considering electric fans with a thermal switch. Would this help my problem? Should I use push or pull fan/fans? Any brand recommendations would be appreciated them.