I need to remember to tell them “the first one doesn’t count!” if I get pulled over in Vegas, and that two or three hours later is a better test. I’m sure I’ll get the same consideration as one of their own.
If you are certain that you are close to the limit, just tell the cop that you regret taking that last shot just before you left. They’ll deliberately delay taking a second test in hopes of you testing higher. That delay may get you under the limit. (If you know you’re over the limit, don’t bother. It probably won’t help.)