Is A/C working normally?

If ambient temp is 90 and you're getting 52° air out of the vents, that's a ∂T of 38 degrees, which is really excellent. The reason it doesn't seem good enough is your A/C is fighting a losing battle with the sun, which is making your car into a solar oven. You will find even a well-engineered and properly-selected and -installed A/C system will have a very difficult time cooling a steel box in the sun unless you give it a fighting chance by keeping some of the heat out. Step number one: thoughtfully pick a good variety of window tint film—not the cheap grey/purple junk; see my comments here—and have it applied. You'll also want to take down the headliner and apply some good insulation to the underside of the roof.