After living in Munich for two years, I learned something about the magical powers of the beer garden: a gravel and tree lined area where you can sit outside with some grilled food and a fresh liter of beer and while away the day.
Now, in Munich, beer gardens can be found all over the place, some, like the Augustiner Keller biergarten seat over 8000 people, mostly self-service style. In San Francisco, the closest you can come to that is Zeitgeist, which can seat maybe a couple hundred outside in the gravelled picnic-tabled garden.
Unline the beer gardens of Munich which typically offer one lager and a hefeweizen beer, Zeitgeist has over a dozen on tap. Though this is great in itself, it does create a small logjam at the bar area, especially when you're dealing with a massive crowd constantly trying to figure out what they want to have next. Here's the trick... when it's warm out and you get to sit in the sun (or shade), any beer tastes good, so pick one thing, get a pitcher of it and enjoy being outside with a tasty beverage.
So, yes. I guarantee if the weather is good, the bar will be crowded. You just have to deal with it. But if the sun is shining and the grill is fired up, having to wait a few minutes to get your drink just shouldn't matter all that much, should it?