Thermostat or Engine Coolant Sensor ?
 

Driving around town this afternoon in my '01 EX, my Engine Temp guage dropped to COLD (5:00), and then recovered normal (3:00) three times. I had the A/C off, windodws opened enjoying the breeze, and there was no indication at all that anything was wrong with the car except the temp guage reading fluctuating.

Both readiator hoses are hot, as is the heater wen selected, so I know the COLD reading on the temp guage is false.

Any ideas or suggestions ?

Sounds like ECT sensor to me. If your thermostat were failing, your temp gauge would go up, assuming your ECT sensor is not faulty.

It's not impossible that both could go bad. The thermostat is gonna be the cheaper part, will probably be anywhere from $17-$40. The ECT is gonna be atleast $25-$45.

BINGO...replaced the ECT sensor (TX97 aftermarket) and Temp Guage is now stable. I'm going to replace the thermostat just as PM , cause it's 13 years old, using OEM Honda part.

You shouldve gone OEM for the ECT sensor. I replaced my ECT last year and it already failed. Its a bit pricier than aftermarket, I paid $70 with tax for one from Honda, but should last for years