Some people will be happy to run the Starter Set adventure....it looks to me like you could get at least five game nights out of it, and with 26 monster stat blocks you have enough stuff to craft an adventure or three of your own if you don't mind the limited range: hey everyone, it's mating season for green dragons in Chirak, so they're all over the place looting gold and cows as gifts for their green dragoness beloveds......yeah nope.
But luckily there's enough stuff floating around to help out. Obviously the soon-to-be-released free Basic D&D rules will offer up 100 pages of material for the core four classes and races, so that's covered. If you would like the latest menagerie of monsters take a look at Dead in Thay, the latest PDF release module WotC produced; it's got a robust bestiary with over 30 pages of monster stats. If you're cheap you can fish around for the playtest bestiary or find it stuck on your hard drive somewhere no doubt.
I suppose you could just make stuff up, too. I'm already considering how easy it would be to adapt Dungeon Crawl Classics to D&D 5E right now, for example. Use the baseline monsters in the Starter Set as examples of design, and it ought to suffice for a few weeks of gaming. In fact just about any old school style module will be really easy to adapt to 5E.
Anyway, if all goes well I may be running some 5E tonight, and definitely this weekend with a game already slotted for Saturday. The system looks good; the basic rules in the Starter Set are extremely easy to use. Maybe I'll run the Starter module, but honestly I love doing my own thing. Still....I guess it would be wise to try the module out, it'll give me something to blog about, at least!