Have a '06 escape problem...water draining from what appears to be drainage hole on engine compartment side of firewall. Where could this be coming from/what is cause?

Or a leak in the heater core.

Sounds like A/C evap drain. If it's near the firewall on the passenger side then it is normal.

have you had the AC on by any chance ,if not then check the drain holes either side at the bottom of nwhere the wiper motor is as their are drain holes either side of the bulkhead or firewall in american ,to drain the floor just drill a 5/16th hole in the lowest point of the floor when the car sits in the kerb this will allow the water to escape i,old adage of mine if it can in then let it out

Yes, the weep drain. Inside the engine compartment, on the firewall, passenger side, half way between top and bottom of firewall. Small rubber tube comes out, then does a 90* turn towards the ground then just stops. You can remove the weep drain and clean it, or use wire to "poke" around and break up the debris. I suggest removing it.

This is condensation from the coil, that would be the water from the air your air conditioner removes as it cools. There is a small drain or weep hole to allow this to drain, this appears to be plugged. With your car safley up see if you can locate the drainage tube, try inserting a small wire up into to clear the obstruction.
I hope this may have helped,
Tom

Clogged AC drain hose.

You can see it by opening the hood and looking towards the back firewall.
Its a short black drain hose and will have a good rust spot under it.
To see it in the car you need to remove you dash. Lower your dash. Remove the screw on the right side and you can pull your dash out. The drain hose is located in the upper left side near the center hub and right near the engine firewall. Its a 6 inch black hose with a few bends and stubs out through a hole into the engine compartment. You can easily pull it out. and stick a short screwdriver up into the drain pan to clean it out.

-- open the driver's door
-- locate where the air conditioner blower box is attached to the passenger side of the firewall - see photo #1 - look to the immediate right at the top of the gas pedal arm

-- condensation flows toward the front of the vehicle through the firewall at the leftmost edge of the air conditioner blower box - drain channel
-- open the hood and stand next to the front wheel on the driver's side
-- look down at the firewall over the battery and to the passenger side of the brake master cylinder - see photo #2

-- locate the small diameter metal lines running horizontally and attached to the engine compartment firewall
-- locate the hole in the engine compartment firewall panel behind the small diameter metal brake lines
-- this hole leads to the drain opening in the air conditioner blower box mounted in the passenger compartment
-- follow the brake lines as they run from under the vehicle and turn toward the front wheel on the driver's side
-- locate the hole in the engine compartment panel behind the brake lines
-- insert a short length of stiff wire into the hole through the engine compartment panel to unblock the drain hole

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-- locate where the air conditioner blower box is attached to the passenger side of the firewall – see photo #1 – look to the immediate right at the top of the gas pedal arm

-- condensation flows toward the front of the vehicle through the firewall at the leftmost edge of the air conditioner blower box – drain channel
-- open the hood and stand next to the front wheel on the driver's side
-- look down at the firewall over the battery and to the passenger side of the brake master cylinder – see photo #2

-- locate the small diameter metal tubes running horizontally and attached to the engine compartment firewall
-- locate the hole in the engine compartment firewall panel behind the small diameter metal tubes
-- this hole leads to the drain opening in the air conditioner blower box mounted in the passenger compartment
-- follow the brake tubes as they run from under the vehicle and turn toward the front wheel on the driver's side
-- locate the hole in the engine compartment panel behind the brake tubes
-- insert a short length of stiff wire into the hole through the engine compartment panel to unblock the drain hole

pull up the carpet and locate the spot from the ac drianage duct insde the car, check for any holes in the floorboard or firewall and reroute the hose out side the passenger compartment, thru the fire wall it may have a rubber grommet covering the hole in the firewall, which can be removed to put duct hole thru.

Was the air conditioning on? Usually water on the floor of the passenger side would mean the AirConditioners drainage hose was either clogged or became disconnected.