Hey Debby!!
I watched the show Beyond Everest or something like that....fascinating indeed!!!!
As to our high altitude......yes, many people actually do get sick! Some more than others, and, of course, some don't. I've taken a few down in the ambulance myself who got sick!!
A lot of it depends upon your physical condition to begin with. Mine is certainly not good, but there IS a huge difference in the fact that I grew up here! I don't feel much of a difference unless trying to hike really up high...we live at 7500 ft. Hubby hikes a lot, but he's getting a bit older and can feel it some when going higher....a lot of water and rest is the key to enjoying hikes.
Actually, when we're on vacation in the lowlands......we were in Texas and Arkansas for a couple of weeks last summer.....coming back home we DID notice a bit of difference for a couple of days!! Isn't that funny??? Mostly climbing stairs, etc. But boy do I LOVE coming back to clean, fresh, cool and thinner air!! I have such a hard time breathing in humidity!! But bring lotion and chapstick.....if you're not used to dry air.....ouch!!
And if you feel ANY symptoms like dizziness, nausea, sudden headaches, blurry, that kind of stuff................tell someone and start going back down fast! Don't ever hike alone!! Of course, that's for many reasons.........
If you mostly are going to be doing city-type and residential activities...then making sure you stay hydrated and rested really are the main things that will keep you from getting altitude sickness. But there have actually been a few cases of people not being able to be at higher altitudes even if it didn't involve a lot of physical activity......but that's pretty rare.
Give yourself a day or two of easy activities and good food (of course!!

) and lots of water. You should be fine.
Soooooooooo............now all that medical lecture over.....sorry, it's the EMT in me!!!

Are you planning a trip out west?? If you are, let me know if you want to try to meet somewhere!! We could have lots of fun!!