2002 Ford Focus AC Leak

Well, It can't be too many things:
either your heater core (or the hoses) is leaking bad, or your AC evaporator (or hoses/connection) is leaking.
If it's the heater core, your car will start overheating when the level of coolant gets too low.
If it's your evaporator, your compressor may not engage if the level of refrigerant gets too low.

Check your level of coolant in the tank; if it's low, the heater core is probably your problem.

Both jobs are expensive.

Check this website for quotes:
www. Repairpal. Com

Also, it will be probably cheaper to have it fixed somewhere else than a Ford dealership. Ask around you to your friends/co-workers, etc for a good mechanic. Independant shops can be very good, but some are just crooks.

Good luck.