You can tell if they are hardnecks or softnecks, but beyond that it gets difficult as so many varieties of garlic look and taste the same, although some are distinctive. Best to ask the seller.
Hardnecks will have a woody stem and a single ring of fat cloves around the stem. Softnecks are usually artichoke types which have multiple layers of cloves, many of which are small and mis-shapened (is that a word???). Most varieties you see at supermarkets are softneck artichoke types, and most are from China. Personally I buy only hardnecks because I prefer large, fat, easy to peel cloves.
The Amherst festival is also a WINE festival, so it may be worth spending a day!
TomNJ