Are you sure you weren't in a bad neighborhood? There are places where that would not have been safe. Are you sure that she was in fact a policewoman?
I believe the LAW says that children CAN be left alone as long as they are in the care of someone 13 years old or older.
I would add my agreement with the last couple of comments -- Sounds like a busybody to me too.
The thing about safety when on a road trip.... Don't forget that every place is someone's hometown and if you use the same awareness you use when traveling in your own hometown with the teeniest more radar to your surroundings -- you'll be fine.
My feeling is that your experience in Orlando was unique. In addition to surrounding area, there may be recent local events which might not be known to visitors.
Another LA suggestion: the space shuttle at the CA Science Center. Sorry I don't have a recommendation for a "star tour." There are many vendors selling maps as well as buses and vans going through neighborhoods.
Note that there are 2 Getty Museums. The Getty Center is reached from the 405 freeway by the aptly named Getty Drive. The Getty Villa is reached from Pacific Coast Highway just north of Sunset Blvd. They are about 30-45 mins apart depending on traffic.
Driving via Death Valley is most scenic but I don't consider Las vegas to Yosemite a one day trip. It's at least a 9 hours drive and that's without stops. Trust me, there are fantastic places on your way. It also will be hard to get a reservation for Yosemite on such short notice.