If it only happens when the A/C is on: It might be that the drain hose from the pan that collects the condensation water is blocked or has come off the little 'nipple' that holds it in place. It needs to be blown out or replaced. If it occurs at ALL times: It might be that the drain that channels rainwater away from the cowl area (the space below the windshield-between the windshield and the hood) might be blocked with dirt or leaf debris, preventing rainwater from draining out and thus, overflowing into the interior thru the fresh air vent which is located inside the cowl area.
It is your a/c condencer ot should be draining out of the truck. the rubber line is more that likely clogged.
The floor in front of your seat where you place your feet.
Passenger side front wheel well
You have a fuse box under the carpet in the front passenger's front floor board and another fuse box under the hood in front of the passenger's side.
in front of the passenger seat under the glove compartment on the floor.
Front passenger side floor (under the hood)
On a 2002 Ford Focus : In the front passenger footwell , behind the kick panel ( there is an access hole )
If it's the front passenger side ,I would say your heater core is leaking .
Heater core failure.
Usually under the floor mat and metal cover on front passenger side.
Under the carpet in the front passenger floor board.
The AC condensation drain is plugged causing the water to back up and leak onto the front passenger side floor.