7,000 MSL is not a high altitude. The pattern altitude at my home airport is 6,800 feet! The terrain rises from there to the practice area, and I have to begin maneuvers so they end 1,500 ft AGL. Most days, the density altitude is above 7,500 on the ground. The cabin pressure on an airliner in cruise is usually equivalent to 8,000 ft MSL. It changes slower than if you rapidly descend from 7,000 to sea level so you barely notice it. I drive to over 10,000 feet all the time. You could do it too, and you'd never even notice. Unless you're flying fighters, there's very little physical exertion required to fly an airplane, so the relative decrease in oxygen with the altitudes you're going to fly out of SoCal is negligible.
That being said, any pilot should be aware of the effects of both hypoxia and carbon monoxide poisoning. From the AIM, 8-1-2.a.2.: "Although a deterioration in night vision occurs at a cabin pressure altitude as low as 5,000 feet, other significant effects of altitude hypoxia usually do not occur in the normal healthy pilot below 12,000 feet." So you can quit worrying about flying at 7,000 feet, unless...
From the AIM, section 8-1-2.a.4.: "The altitude at which significant effects of hypoxia occur can be lowered by a number of factors. Carbon monoxide inhaled in smoking or from exhaust fumes, lowered hemoglobin (anemia), and certain medications can reduce the oxygen-carrying capacity of the blood to the degree that the amount of oxygen provided to body tissues will already be equivalent to the oxygen provided to the tissues when exposed to a cabin pressure altitude of several thousand feet. Small amounts of alcohol and low doses of certain drugs, such as antihistamines, tranquilizers, sedatives and analgesics can, through their depressant action, render the brain much more susceptible to hypoxia." So, don't smoke, don't drink (or be hung over), and don't take any medications before flying (until you know exactly how the medications affect you). The AIM isn't the easiest place to read this stuff; there are lots of other resources available in books and online regarding hypoxia and carbon monoxide poisoning, ear blockage, decompression sickness after scuba diving, and lots of other good things pilots should know.
When I was in the Air Force ROTC years ago, we all got checked out in the high-altitude chamber so if an "incentive ride" in a fighter ever came around, we'd be eligible. Of course, none did, they always went to cadets in the Academy. It was still fun, though. The main thing I remember was the tunnel vision and loss of ability to see colors. They'd crank it up to 14,000 feet and give you a color wheel, and you could pick out maybe 3 or 4 basic colors. As the altitude started coming back down, you'd realize there were maybe 14 other colors on the wheel you couldn't see at altitude! We weren't in there for very long, so the loss of coordination, blue discoloration of lips and fingernails, memory and alertness, and other affects of true high altitude didn't really kick in.
Position and hold