Will high winds rip off vinyl siding?

Most siding installation is rated for winds up to 110 mph. If wind does rip it off, note that vinyl siding is much easier to re-install than other types of siding.

What's it means when the salesperson talks about a "square?"

A square is 100 square feet of siding (10 feet by 10 feet). Individual square footage is not used.

I hate power washers. Do I have to use one to clean vinyl siding?

No. Actually, you're better off with less water pressure. Just use a garden hose, a soft-bristled brush, and diluted solutions of Fantastik® or Windex®. Solutions of vinegar (30%) and water (70%) will also do the job.