The AC (3 tons) in the home (about 1600 sq ft) I am renting was replaced less than a month ago.
Thermostat setting: cool to 78 deg F.
Average outdoor temps: Day 105 deg F; Night 82 deg F

Observations:
1) Temperature never goes below 81 deg F, even at night.
2) Air coming out of the vents does not feel cool.
3) High pressure line both near the indoor evaporator & the outside condenser do not feel warm.
4) Low Pressure line both near the indoor evaporator & the outside condenser feels cool (but not as cool as the ones my neighbors' home ACs).
5) Low pressure line both near the indoor evaporator & the outside condenser do not sweat.
6) Unit just keeps running but since the target temperature is never reached, the unit never stops.

What the AC technicians said:
1) Thermostat was not set properly.
Action Taken: I had the technician set the thermostat himself just to make sure.
Result: No change in AC cooling performance

2) The filters need to be changed.'
Action Taken: Put in new (regular) filters both at the evaporator & at the door leading to the space where the evaporator is hidden.
Result: No change in AC cooling performance

3) The temperature outside is too hot that the AC can't keep up.
Action Taken: Added insulation to the doors and windows where warm outside air was probably passing through.
Result: No change in AC cooling performance

4) Freon not enough
Action Taken: AC tech took measurements at the condenser & said that the freon levels were OK.
Result: None since the property manager did not want to add freon if levels were OK.

The property manager says that since the AC techs already checked the system twice after the new unit was installed and did not find anything wrong with it, she can't do anything else for me.
That is unacceptable since my neighbors' ACs are the same as ours and whose houses are of the same size and yet their homes are cool, even during the hot afternoons.
Mine does not even go below 81 at night.
I wake up in the morning before the sun rises and I'm lucky if the temperature gets to 81 deg F.
I suspect that either the AC unit was improperly installed, that they failed to do something, or something was improperly done.
I think I'll be better off opening the windows and turning on the ceiling fans.

I would like to know what other things need to be considered based on the observations I made and what else need to be checked.
It's really uncomfortable at home, especially during the mid to late afternoons when the indoor temp goes up to 90 deg F (in spite of a thermostat setting of cool 80 deg F).
My electric bill is almost double of what I normally get... I expect the next one to be higher.
On top of that, I have a 14-moth old baby at home.
Please help!