Rnch knows what he's talking about - and yes, the Marigny, particularly Frenchmen St., is very walkable from the Quarter. Just walk downtown (sort of east) on Decatur St. And you'll find yourself on Frenchmen the moment you leave the Quarter. I personally wouldn't recommend going much deeper in by yourself on foot - the layout can be confusing to a newcomer - but you should have no problem making friends who can bring you somewhere.
And for the love of god don't drive in the Quarter on a Saturday night. You are asking for so many problems and you will never find a parking place again. Just park at your hotel and walk.
If you decide to go a more mainstream route, most of the Saturday action in the Quarter is at the Bourbon Pub and Oz, both at Bourbon and St. Anne, both charging a $5 cover until around 2am, both overcharging for drinks (but Good Friends one block away is very affordable), and both hitting their stride around midnight. Lots of uptown and mid city 20-somethings. Oz is your typical flashy dance club, Pub is a loud, crowded sit-down place with a dance floor upstairs. Anyone there can tell you the full list of other options.
Alligator is just about always expensive... Some of the best food in the city comes from holes in the wall, though. Maybe Praline Connection on Frenchmen, and while I haven't tried it, Daisy Dukes in the Quarter supposedly has a good (and def cheap) alligator po-boy. Just recently off the vegetarian wagon so meat recommendations aren't my forte.