I'm pretty sensitive to getting the best out of playing these games as well. Here's an answer from someone who just finished his first play-through a couple of minutes ago:
Either setting is fine, but out of those I would choose either the dark or the intimacy of a bedroom.
I've never played games intoxicated, but I believe I'd still choose to play this sober. Flower's not really the game to trip out over (flOw would be much better for that).
I suggest playing it alone. Maybe a girlfriend would enjoy watching too.
On another note, Flower plays in multiple segments but can be finished in one sitting. My main piece of advice is to relax and take your time as you play so you can absorb the game. Don't worry about rushing to complete it.