First, shame on me for travelling without a credit card, double shame for travelling with a child without sufficient cash or cards. Hopefully I remembered to bring my cell phone - even the most cash-strapped traveller these days seems to have a cell phone.

Big box store (modulo size of crowds, their mood, and the severity of the event): you're in a desert, obvious buy is water and/or containers, based on availability and whether uncontaminated water could be expected from the tap nearby. 6-9 gallons if you can get it, or equivalent containers if you cannot (consider empty 5 gallon buckets from hardware or housewares since they may not be flying off the shelves as fast as the 24 packs of Dasani and diet Coke). In a pinch, a couple garbage bags one inside the other and a sturdy scavenged cardboard box will hold lots of water in your car. 2 days inexpensive, non-perishable food for the road, if you can get it. No phone card - public pay phones are scarce in every direction out of town. If no cell phone, consider the cheapest TracPhone and 100 minutes. You probably won't be able to charge and activate it until you get out of Dodge, however. A knapsack to carry water if you find yourself on foot might be extravagant, a poly-cotton sheet to fold into slings or some cord to hoist water carriers a bit cheaper.

If the big box store has been beseiged by long lines and/or angry mobs, leave as unobtrusively as possible. Your ultimate destination is irrelevant, your first vector is towards safety, resources, communication and assistance. I'd scavenge or grovel the trash bags/boxes at an eatery, fill with water, then hit the road and head for St George Utah. On less than a tank of gas you'll get there, or be able to stop at one of a few oases where you might gas up and regroup. And under normal circumstances the route is well patrolled by Nevada and Utah highway patrol, well-travelled, if you had to stop you wouldn't be alone.

I'm with some of the other responders - unless you live in a total, resourceless vacuum or your family and friends are caught in their own event, you reach out to them from St George or on the road from Vegas. Let them know your route and ETA, that you'll need money wired there, accomodations at the Holiday Inn if they can get it, and a Delta feeder flight out of St George if possible. They can watch CNN and the Internet to assess your possible progress, call you back on your TracPhone when in range, and add minutes to it. They might as well start the process of adding you to their own credit card and ATM card so it can be mailed to them and sent to you. You may not be home for a while.

Lots of folks will head to LA, but lots are going to be headed in the same direction as you. Depending on the event there may be water/gas trucks positioned, and refugee shelters set up along the way at the AFBs - but don't count on it. Regardless you'll have plenty of company in St George, but there will be resources and there should be a supply line going in there sometime after you arrive. fwiw the people I've met in St George are some of the friendliest people on the planet, you can expect general compassion for any person protecting a minor child.

Side-thought: if my employer had *any* presence in Vegas, I'd try to call there or visit if reasonable and safe before leaving town and see if they could offer shelter or assistance. My employer does happen to have a Vegas sales office, unless the event closes it, odds are good they or a call to the main office would get me on a short list of people they want to help get to safety.

If you were really running on $250, driving straight through to any of these final destinations may not be feasible (20mpg doesn't account for hours of air conditioned idle time in stalled traffic, gas shortages and price escalations en route, weather or desert-inspired car troubles etc). Your ability to maneuver a rental Saturn sedan on anything unpaved is questionable and not advised anyway in desert conditions. Don't panic.

No one on these boards wants to admit it, but in this scenario you are a relatively unequipped and child-burdened refugee when you leave Las Vegas, and you should be at least partly prepared to live like one. Yes, if you actually beat the crowds you might gear up on the cheap at the big box and Rambo yourself along neglected paths to distant cities, you might even get moving out of town before cars begin to block the highway and slow you down. I contend your main job is to equip yourself and your young friend with food and water and get the kid to safety - wherever your best sense of the situation tells you that is. It might be Red Cross, it might be National Guard bussing you to a base refugee center. If you successfully self-evacuate, you may be in St George for a while and reach your destination only after the event response kicks in. Then you can be FEMA evacuated to home. Pride goeth before the fall. Its the kid that matters. I would only feel defeated by relying on the authorities if I had headed down to Vegas as well-equipped as I am closer to home.

Cheers,
Lono