Late on the thread! Oops... but
i <3 beer. My b/f and I consider ourselves "Beer Enthusiasts" we are out there! Just like your wine fanatics- there are beer fanatics! And I am more than happy to answer any questions you have about beer! lol.
To start off, there are valid reasons NOT to drink. But you can drink responsibly. I generally get beer and drink at home with the b/f or when friends are over- we love to bring over new beers to try! I either have a cab or a friend drive me home from local brewries or beer festivals, and I dont drink more than once a week, and I
attempt not to get drunk. (Been there done that, now I just enjoy the beer)
I once drank only zima and margaritas... I made the leap into beer hood with GOOD BEER.
For GOOD REAL beer, not mass-produced, in-it-for-the-money-not-the-beer beer is either a
widmere heff or pyramid heff. Heff is a good starter beer because it is a wheat beer (and we are all familiar with wheat) and has citrus flavor added to it. Yum! From there you can move on to malt, barley, or hoppier (Hops are for the REAL beer mongers- i dont like hop beers, but the b/f does so I've tried a few) beers, but the WHEAT beers are a good starter.
Go for anything with wheat. I personally dont like the yellow, lighter beers because they are a bit watery, even the local brewed lighter beers- I go for amber-ish in color. If you have a wheat beer, it will be a bit cloudy- that is good!

Try adding a squeeze of fresh lemmon to them!
Blue Moon is decent, but it's produced by Coors.... I consider it a beer that is only good for people's first step outside of the nasty mass-produced beer, Blue Moon is a baby step for people to get away from Coors, Miller, Bud etc.... I highly recommend AGAINST any of those unless you are going to a toga party and plan on puking it all up at the end of the night- NASTY BEER!!!
All I can stress is if you just want a beer to drink out with your friends, not to get trashed, but something to go with a meal etc.... Get beer from a company that has heart!
My personal Fav Breweries: Shiner (TX), Pyramid (WA), Widmere (OR), Unibroue (Canada), Victory (PA), Red Hook (WA)
Again, stick with the wheat beers- malt and hops can be a big turn off to your margarita-loving pallet. But once you get a taste for the wheats, you can explore the other side.
Heffs are a great starter because they have a yummy citrus taste. Considering you like margaritas and those are citrusy- start with a heff! =D (You can get a pyramid or widmere heff almost anywhere, and I've visited both breweries- great companies, good food- lots of heart!)
Lemme know what you think!