I've found both hybrid and heirloom seeds locally. Just look on the package for "heirloom". If it doesn't say, assume it is a hybrid, or go research the name of the variety or call the seed company in question.

Seeds grown from a hybrid will sprout just fine, its just that the special charactaristics of the variety they came from may or may nor be present in the new plant.

An heirloom offspring will be more of less the same as the plant it came from, assuming it wasn't pollinated by pollen from another variety in which case you've just created your own hybrid.