First, Harley dealers are probably the last places to go for any mods. They will try to sell you their own products, which are overpriced and under performing. A set of mufflers won't void your warranty. Check with owners here for the best ideas and info on parts.
If you're military, I thought you could register your bike out of state. You can pretty much do what you want, and I would bet there's not a cop in Cali that would cite an active duty service member for noise violations unless you were riding like an a-hole to start with. Whomever you're hanging out with probably think of themselves as some kind of Hell's Angels (wannabes), and have an anti-authority mindset. ANY regulation is EVIL!
I've lived in half a dozen states and a couple foreign countries. I've loved every place I've lived, and everywhere has their pluses and minuses, And frankly, Cali is one of the best places, by far. Look at the advantages: You can lane split legally, and literally ride to many manufacturers' factories to buy bike equipment directly from the source, and get info directly from the manufacturers. Painters and mechanics for Harleys are everywhere, and I have five dealerships within an hour of my home, in case I have a breakdown or have a specific model/part I need. Beaches, mountains, deserts, coastal highways are everywhere here, and there's more clubs, riders' groups, and support here than anywhere else. Mexico has some great riding ares too. Did I mention the best weather in the USA in San Diego?
Hippie state? If you ride an hour from the coasts, you'll find some of the most conservative people in the US. I lived in Utah for 7 years, and the area of California where I live (2 hours from San Diego) is even more right wing than Utah, if that's possible. If you're feeling home sick, you can ride to the central and western parts of Cali, and be surrounded by enough mullets, rednecks, and Tea Partiers to make you feel right at home.
As far as regulations, the US is behind every civilized country in the world in regulating our behaviors. With 35 million people and 100 million cars, of course Cali is the first to need to adopt regulations, and the rest of the country follows suit because they need to, not just because evil California did. Get out and see as much as you can. You only live once!