Hi,
have you tried to reverse your coolant ratio e.g. 70% Water and 30% Coolant?
You might be surprised on the effects!
Being in South Florida the only concern is to lubricate the the parts involved with the cooling system, but absolutely not about freezing.
Just an other thought.

Deleted misleading paragraph completely.

I took the link off, since it wasn't representing the real thing.

EDIT:
I am sorry I didn't see it clearly in the photo. The resistor is in parallel to the switch (NTC). A much lower value might trigger the FANS earlier, however the fan(s) do draw quite some current and the 1/2 watt resistor could burn away at lower resistance.

I would have to check with the wiring diagram, since there might be a relay involved!

Hope I didn't get too technical with my reply.

OK, just had a quick look at the control circuit.
As it looks the Temp Sender unit is communicating with the ECM (Engine Control Module)
In return it switches the FAN via relay (in Relay Box) at a elevated temperature on.
If the temperature rises further, it switches the second FAN via relay on.

To fake the hot condition, you would have to unplug the connector and put a, probably 1K resistor between the pins. The Value, I only guess if the cold resistance is 10K.
The 1K may be less, possibly in the 100 Ohm range. The ECU is probably reading a 0-5V DC so 5V/100 Ohm = 50 mA of current. 5VX50mA = 0.25 Watt So a quarter Watt resistor will do.
You can test the auxiliary FANs just by idling the engine and put that 100 Ohm or the 1K resistor across the pins. If they come on, I would do this permanently, but your fans would run at all times and I don't know if the ECU would catch this and throw an DTC at you. Remember, the higher the resistance the less power is dissipated across the resistor, so a quarter watt or higher does the job.
MAKE SURE THEY STOP ONCE THE ENGINE IS OFF!

Putting a different value across the Temp Sender Unit, would work too, but the ECU might throw an over temp warning at you.

__________________
Mostly, I don't know notin, I just know where to look.
I am looking back, to over 30 years in Electronics Design.
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95 W124 E320 M104.992 - Because, I love to repair, naaaah!
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Cheers,
Norbert