I wouldn't worry too much about being put on some type of watch list. There is lot of flow over from security professionals that attend Blackhat the preceding week (costs a lot more). They usually have a "meet the fed" talk to address any interest the government has in the conference. My group were involved with IT and so were the people that I meet.

I attended Defcon 16 and here are some pointers I picked up from that:

You will miss the first day of talks (Friday) if you end up drinking till 5:00 A.M. the preceding morning and talking with a bunch of hackers. In defense, that really was the best talks I attended.

Friday is usually the best day for talks.

Seriously consider using your smart phone as a tethering device if you must surf the internet on the laptop. Take a look at pda.net. Additional points are awarded if you use an XO.

I can't attest to this...but try to avoid using the ATM next to the bar in the Riveria. I had some strange charges show up that week from someone using my pin in California. Coincidence?

Try to use a bathroom not located inside the conference. The sewer smell from backed up pipes was not conducive to an enjoyable experience on Saturday...especially with some lingering effects from Friday.

See if you can get you trip written off at work as Security Training. Try to be suave when you explain that the receipt will come in the form of a big a$$ badge that looks like a blinking motherboard.

Never trust that a hotel (not the Riveria) will keep your paid for-the-weekend room reservation if you don’t check in beforehand. Even if you call stating that you will be in late (even if you weren’t expecting to show up at 5:00 a.m. – which did make for an interesting conversation with the hotel manager. Still it was a nice room upgrade…I guess ;-)

You definitely want a t-shirt.

If you don’t base yourself at the Riveria or Circus Circus, seriously consider a car rental in your budget.

I’m sure there is more advice I could give. It is Vegas after all.