DC Diaries: Day 1. It was all going so well...

I arrived in Washington DC around 1:20pm this afternoon. The group proceeded to the hotel, and because I am the only female out of 10 students from our group at this conference, I was given the option to get a room for myself, which I took. For some odd reason my room ended up being in the far end of the building, an old wing of the hotel where nobody else was staying. This turned out to my advantage because my room is so much nicer than everyone else's. It is very cozy and quaint and I feel like am staying at a fancy bed and breakfast in upstate New York.
Immediately after arrival we proceeded to the Conference registration, where they already had my name and there was a goody bag waiting for me. The goody bag contained a CD with all the technical session presentations, a program with the schedule for the week, and oh goodness there was freebie in there too! A gift, if you will, something to make this week even more unforgettable. What could it be? well if it isn't a money clip!!! How lovely no? I opened it in front of the registration personnel (all women) and said out loud "are you serious? a money clip? how feminine!" And of course, I was right, so the ladies in the registration staff laughed out loud. I promised to myself and my colleagues I would write a serious note recommending a more unisex gift for the future, and I will drop my money clip with note attached in the suggestion box at the end of the conference.
The afternoon went on, I found a few of my friends that I used to work with/for at the University of Illinois. I invited them to my talk, though also admitted to them I was quite nervous because green energy is a hot topic right now, so I can foresee a lot of people attending it. Anyway, some of us decided to ditch the plenary session and go grab some food and drinks. We ended up at a sushi restaurant across the street, sat on the floor, ate some sushi, drank some beer, it was a lot of fun!
After dinner we decided to head to he corporate exhibit where corporations strut their stuff by showing all the latest technology/products. There was free beer and wine at the exhibit, one of the main reasons we were so inclined to attend. I grabbed a beer and started walking around. At some point I start talking to a French man from a certain semiconductor company I will not mention. I thought we were having what I would call a competent discussion on his flyback converter controller chip, that in this case was being used to drive the circuit of an LED lamp. He asks me where I am from, and I say Venezuela, I ask him where he is from he says France. He also introduces me to his other French colleague standing nearby and all of a sudden says "Are you over 21?" I looked at him, a bit offended and said "Yes, of course I am over 21, I am in gradschool, why do you ask?" he says "well, I just see you with this beer..." Now don't get me wrong, everybody was walking around with a beer, and mine was mostly full!! His other French colleague steps in and says "please don't mind him, it's a little French humor" and proceeded to ask me some off the topic question about my work, I politely answered it and then I said "right, well it was nice to meet you both, thank you for sharing with me about your chip" I shook their hands and left.
What... the... f*ck? This would NEVER, EVER, happen to a man no matter how young he looked like. This is the kind of attitudes that make me want to strangle people!!!
I went back to my friends and told them about it, they said the French man was a douche and suggested I forget the whole ordeal. Then they started a joke out of it, which made me laugh, bless their souls for making me laugh. Now every time someone does something seemingly dumb we ask "Are you over 21?"
I just came back from a game of darts at an Irish Pub and even though I already let it go, it still makes me kind of uneasy to know that I will always encounter this sort of disrespectful sexist attitudes in my workplace. I honestly don't know how to interact with these people and would love to hear some suggestions. I don't need you to agree or disagree with me, I just want to know what you would do.

Currently feeling: frustrated, still a bit angry, or maybe just annoyed
Currently listening to: "All Alright" by Sigur Ros