Showing up? Sure..staying and buying something (which is the point of the garage sale)? No, not regardless of what the host of the garage sales does. On that note though doing a 'drive-by' (the nice definition of it lol) also means someone shows up but doesn't stay depending on what they can see is available. To the underlined thing..actually yeah you can def. know ahead of time what is priced. Many times here when people hold garage sales they'll advertise on Nextdoor (social networking site) or for my neighborhood area eNeighbors (also a social networking site). They'll use Craigslist too. Would you know everything? No. But you can know some things.