IMHO, without spending enough money for a week vacation in the Caribbean, a windshield mounted Escort is good enough. I picked one up last summer and works great. I think it's the 9500 red series and payed about $200 or so, can't remember exactly but got it at Best Buy.
The best way is to be tactical about speeding in this country. I had my M3 in Europe for 3 years before moving to the States. On the freeway, the radar detectors are great because you'll pick up the signal (RF's) from a long distance before the cop can make out who is speeding if your near other vehicles. If in city, it's better to just flow with the speed of the traffic or/and just slow it down. Not worth the hassle.
Even if you have a jammer or can evade the laser/radar. A cop seeing you do twice the speed of the rest of the traffic can still get you on reckless driving. He/she does not need to actually have a speed registered. So just watch out. I speed all the time and knock on wood, it's been almost 20 years I don't get zapped because I'm a bit more tactical about it. Good luck!