If I hit the AC button to shut off the AC, the temp in the vents then gets hot, if I kick it back on, it is cooler than the outside/nonAC air, but it isn't 'cold'. The system worked great last summer...

 

But when you change the temperature **** position, does the temperature change?

The blend door (aka air temperature door) regulates airflow over the heater core. If it is stuck pushing air over the heater core, there is only so much the a/c evaporator can do to cool it before it just gets warmed back up again.

Here's a schematic of the '01 manual hvac system for a visual:

 

If I turn the AC button off, then turn it to HOT, it gets hot. When I turn it back to Cold it gets a little cooler, blowing outside air, then when I hit the AC button, it gets a little cooler still, but still not cold...

 

Does the smaller line under the hood get cold?