Welcome to the forum and thanks for the question!
First, check out this page. It is the cooling system fan details for a 2001 model, but I think they are pretty much the same.
Cooling System Fans
My questions are?
1. Is there any way to test the relays without buying new ones. And how many control these fans.
2. Can I hard wire the fans to see if they work.
3. If the sensor is bad, will it cause the fans not to turn on.
1) There are three (3) relays. I believe the easiest way to test the relays would be to switch the Air Conditioner ON.
As long as you have refrigerant in the A/C system, this should turn the fans ON (could be low-speed or high, depending on the refrigerant pressure). You should also be able to SWAP relays around, as long as they are the same part number. There is a link to the relay diagrams on that page I mentioned above.
2) You could directly connect a battery to each of the fan connectors to test them. But if switching on the A/C turns the fans on, you won't have to do this.
3) If the Engine Coolant Temperature (ECT) sensor is not working right, it could keep the fans from turning on at the right time. There are some testing and troubleshooting steps here
I almost forgot - The symptom you mentioned (temperature gauge going to about half way in traffic) is the same thing my van does. It usually goes just above the half way mark while stopped (traffic or drive-thru) and then go back when I start moving or switch on the A/C.