'87 SDL a/c runs when it wants to!

[DSLinTampa]

I have looked in the forum and searched but haven't seen something just like this, so here goes:

My light blue beauty has had weak a/c since I bought her. 'bout 240,000 miles now; runs like a top. a/c has been charged several times. It seems to run pretty well and coll the car ok when it is not hot outside. However, I live in FL and it is usually hot. If I run the a/c during the day, it may or may not engage the compressor. If the compressor engages, it will usually just disengage at some point, often at a hard stop or after idling for a while. I can feel the change in the engine. After it disengages, I can often stop and restart the car economy, then switch to a/c, and it will engage again.

Also, I get no air at all (a/c or econ) out of the center vents. What's up with that? Defrost, a/c, econ, all blow through the window and side vents. There doesn't seem to be any change when I press the floor button either.

Finally (I didn't search for this one, so kill me if you want), where is the a/c drain for condensation and how do I unclog it? Apparently all the water is draining into my passenger compartment! Heard it sloshing last night.

Thanks in advance.

BTW, I am fairly handy with cars, but have limited access to tools, so if someone knows a knowledgeable and fair mechanic in the Tampa bay area, I would appreciate it.