I have power steering and it has a cooler but my brothers doesnt need one and i was wondering its needed or not
Since it gets pretty hot where you live, I would keep ( or get the cooler ). It will help keep all the components that have fluid in them ( hoses, ram, control valve, and pump ) to last longer.
I just installed a rack and pinion power setup on mine, using modern parts (~93 mustang GT), and I did not install a cooler because the parts houses said there was not one on that model car. I don't plan on doing any autocrossing, pretty much highway and straight-line driving, so I did not install a cooler. I figure if the fluid starts to look or smell bad, it would not be very difficult to slap a cooler in-line at a later date. If I already had a good cooler in the car, I would leave it. It definitely will NOT hurt, and may actually be beneficial. Cooler fluids are always more efficient and last longer.