I have a problem with A/C.

Hi guys, It has been about 3 weeks since I bought 2009 Aveo LT(with manual lock and window) as my first vehicle.
I bought it very quickly without having enough time to inspect any problems. I was not very patient.
While I drove it to my apt, I found that the A/C was not blowing cold air. So I brought it to a certified A/C mechanic. He said the expansion valve seemed to be clogged. We replaced it, then it got better but started to blow hot air again. He said the previous owner probably used the recharging can which contains some kind of chemical that causes clogging the system. We tried to clean the new expansion valve and it got better(best condition so far). It now gives "cool" air HOWEVER I need to drive for more than 5 minutes to get cool air and it is just not cool enough. A/C should be blowing "COLD" air but mine just blows cool air which just can't decrease the temperature of the inside.

I live in Southern California and hate the super strong sunlight. I really want an A/C that works perfect. If any of you could give me just a little help, I would be very thankful.
Sorry for my poor English.
Thank you for reading and sharing your thoughts.

Can you take your car back to the certified mechanic that fixed your car and ask him to measure the pressures on the low and high lines and post the readings? He should you do it for you for free.

If the pressures are OK, check the ambient temperature sensor, on the front, behind the grill.

It takes about 5-10 minutes to get COLD air with my 188k-miles car, so maybe thats normal for a cheap car or a weak compressor? But then again I jerry-rigged my car to make it work lol

For me, at roughly 70F, the A/C takes less than 5 minutes while driving, but above 75F, especially above 90F, it takes 5-10 minutes while driving.