Thanks for your holiday greeting! Fourth of July has always been one of my favorite holidays - an afternoon filled with cooking food outdoors on the barbecue, enjoying a cold beer (or two or three.... ) and just generally having a very relaxing good time. When it gets dark enough outside, the fireworks begin. Every city/county/metro area usually has an "official" firewokds display, but that doesn't stop most folks from shooting off skyrockets and such from their front lawns. (Mind you, fireworks are technically illegal in many states, but that does not deter anyone. My brother is a major fireworks fan, and we've often seen a police car cruise by as he lit a Roman candle and the cops didn't do a thing about it.) I'm lucky that my in-laws live in Georgia, and when we visit them we have to drive through South Carolina which has some of the most lenient fireworks laws in the country. We always stop there to pick up an array of "explosives" to bring home to my brother, who uses them to put on a fabulous show for us every Fourth of July.
I believe I've rambled a bit....back to the original question, "Happy Fourth!" or "Happy Fourth of July!" are common greetings. When you're out shopping on July 3, buying groceries or gasoline or whatever, it is typical for merchants to say "Have a great Fourth!" as you pay for your purchase.