I think online dating can be a good experience if you just look at it as a nice way to meet new people and can be a good way to practice being the real you. Who cares what someone else thinks. Just go in and tell yourself worst case scenerio is you meet a new person and you may not have much in common but how will you know till you do it.
Dating is a lost art. Dating is just doing social things with someone. Don't confuse it with a relationship. And since I've done it, I would also say absolutely under no circumstances go any further than just a date if you know what I mean. The alternative will just complicate things plus that's not what people who respect themselves do. I've been there so I'm not assuming anything about you...just talking about me.
As far as the drinking thing while doing it, only you know if this is going to be hard for you. But they way I look at it is if I can't be real with a stranger who the heck can I be real with? What do I care what they think. I care about people who care about me think.
Have fun on a date but it's just a date. Hold your ground and stay away from drinking. If the dude can't handle a movie and a dinner without having to drink...move on to the next one who can!
Good luck! There are nice people on those sites but everybody has to go through a few question marks to find them.