I like 180. Colder is not automatically better. If it were, we'd just leave out the thermostat and run as cold as possible. An aluminium housing is a nessessary upgrade as well. Save a little bit of weight, doesn't rust, and no galvanic corrosion.
On your coolant, since you're in FL, I'd do RMI and water. As long as you keep an eye out for random global warming cold snaps that get to below freezing.