I live in one of the two states where marijuana is legal. However, it's still not legal, even here, for people under 18. And THC is detectable in your system for 2-3 weeks after you use it -- so if something goes pear-shaped while you're flying and you end up getting investigated by the FAA, you could still be in deep trouble even if you haven't been high in days.
Remember, too, that the FAA is a federal agency, and doesn't care one whit what the good citizens of Colorado and Washington think should be legal. As long as you're answering to them, you need to consider yourself governed by federal drug laws, regardless of what state you're in.
So keep off the grass. Seriously.
If you want to drink with your buds, remember that it's not the drinking that gets people into trouble: it's doing it in stupid places with stupid people, and combining it with other stupid activities, like driving. It can't be overstated: if you're going to indulge, make sure you are in a safe place with safe people you can trust. Do not drive or leave your safe place until you are sober. (You can get a keychain breathalyzer to check this.) Do not fly for 24 hours after your last drink - personally, I ground myself for at least 36 hours, just for the extra margin.
It's good that you're already cultivating the good habits you'll need to protect your entire flying career. You sound like a great kid with very sound judgment. Remember that you're aiming higher than a lot of your friends are right now, and that means that you're also choosing a higher standard of self-discipline. It's not always fun, but the rewards will be more worth it than you can imagine right now.