I crack my whips wherever I happen to be. My side yard, (very difficult. Lots of trees in the yard,) at a local state park or one of our many college green, sometimes a college lecture hall.
My current favorite place to go is up to the Ridges.
http://www.forgottenoh.com/Ridges/ridges.html
It's is the "University Name" for the several acres of property and buildings that used to be the Athens, Ohio State Mental Asylum. It was donated by the state to Ohio University back in the 80's, (because the state couldn't pay for the upkeep, and it was easier to give it to OU,) and most of it has been converted into administrative offices for the college, (so it's job as a nut house, hasn't really changed.)
I go up on the front lawn of an abandoned building, the old Tuberculosis Ward, which overlooks the rest of the facility and work up there. It's very secluded and people tend to leave you alone, but it's also VERY visible from the road and nearby buildings, so people don't mistake the noise for gunfire. OUPD has driven by on routine patrol several times, and never batted an eye, other than to stop and watch because the cop was interested.
The Ridges is also purportedly one of the most haunted places in North America.
I also sometimes practice targeting in my living room.
This is with 6 and 8 foot whips, by the way. Working in that confined a space teaches a lot of control, and I find I'm SO much more accurate when I have space to spread out!
That last location there by the way has a price, guys...It REALLY helps if you're a bachelor. A year ago, there's NO way I'd have gotten away with what I do now! And my parents have this nice, long room with high ceilings at their place. It's very tempting, and the couple times I didn't think about it and cracked a whip in there, I got yelled at like I was 6 again. Not that I blame them! Me and my "Outside Toys..."
I suppose it could work the other way though, and it's not just that you have to live alone to crack whips in your living room. But remember this: If your wife, girlfriend, or significant other lets you crack whips in your living room, SHE'S A KEEPER! DON'T LET HER GET AWAY! ;-)
All the best, happy cracking, and DON'T BREAK ANYTHING! ;-)
-Dan