A) The event itself starts on Friday, July 30th and runs till Sunday, August 1st. There are things to do before Defcon starts, but they are not official events, and unless you are cool, people won't want you to be there... Also, Black Hat runs before Defcon.
If you are new to DefCon I recommend getting there on Thursday July 29th and attending the DefCon 101 Session to learn all about the things going on and to do as well as some get some advice on surviving DefCon.
A) You have to be 18 to register a room at the Riviera.
A) DefCon often negotiates a pretty good room rate for its attendees. The rooms for DefCon 18 cost $99.00
A) Why do you want to register an anonymous room? Oh, I know... Because you're a Tool.
A) Yes, unlike at the Previous hotel, registering on the website usually guarantees you a room, though it's always best to call prior to the con to confirm reservations.
A) Due to Vegas trying to be more "Family Friendly" (read: bitches) smoking is only permitted in the casino proper, bars in the casino area, and designated outdoor smoking areas. 80% of the hotel rooms are nonsmoking. Oh and "Whiney non smokers can kiss my fucking ass".
A) With the amount of rooms at the Riv there really is not reason not to try to stay at the Riv. If you decide to goto DefCon late and the rooms are sold out there are plenty of good hotels around the Riviera.
A) No, don't be a fucktard. If you call hotel security and people find out about it, they may be pissed. Is pissing off a bunch of hackers really how you enjoy spending your days? Go buy some ear plugs/nyquil... On second though, you shouldn't be fucking sleeping, this is DefCon. Get the fuck out of bed and go join the party.
The common ones folks use are Circus Circus right across the road and The Hilton.
If you are really tight on cash, try a youth hostel:
1) http://www.hostelsweb.com/hostelsweb.com/hostel.php?HostelNumber=825
2) http://www.hostelsweb.com/hostelsweb.com/hostel.php?HostelNumber=5997
A) The rooms are about as secure as any other regular hotel room. If you have anything expensive you always run the risk of having that shit stolen from you when you stay at a hotel.
A) There are plenty of places within walking distances of the riv where you can find food.
A) Spending Money (not including room): Should be $140 for the badge. Money for food, alcohol and swag. You can squeeze by with $400. Less if you budget really well.
A) Cabs usually sit at the airport, so you should be able to walk out and get a cab at the airport. If you are going from the Riviera to the airport on your way home, it takes 4 hours hangover time. For Taxi Rates check out: http://www.taxi.state.nv.us/FaresFees.htm
A) Give the hotel a call. Though you do run the risk of them filing for chapter 11 within the next year and you losing your deposit.