Unwelcome Americans is not the right description of the Buda crowd! Unless you're bringing the Donald
The quarantine would very likely be for everyone arriving on plane, not just Americans. I cannot imagine that certain countries will be singled out, that would cause a massive political backlash. There is certainly a chance that the quarantine will be lifted by September, if infections go down. The problem is, however, that no one really knows what will happen. If you're the type, who is flexible and can make up his mind on short notice, you may very well get more done than those, who like to plan ahead.
As for age and risk groups, I have a slightly different opinion than mainstream wisdom. The chance to catch the virus is the same for all, your age and pre-existing conditions don't came into this. Whether (and indeed when) you get it is mostly determined by your behavior and a little luck. And
if you get it, you have a non-trivial chance to either die or suffer longterm effects - again, no matter your age and pre-existing conditions. Too many young and healthy people have reported mid-term effects already and science has found irreparable damage to the lungs and hearts of people, who did not even have symptoms or very light symptoms. If you ask me: avoid this one like the plague. But I'm no expert, this is just a hunch.