well, my first time I smoked, waited about 20-30 minutes, went to the movies(The Departed), fell asleep in the movie, and after that went home completely fine. So about 2 to 2-1/2 hours I was fine to go home. If you have 3 hours to sober up, you'll be fine. When you get home, shower.
Make sure you set an alarm or something to wake you up if you fall asleep. Do that before you smoke. Then, and most importantly, get blazed and have fun.