Munchen this spring.

Airfares are low from early Jan to late March, then start to rise... United for Burlington-Munich, for example, offers low-season fares 09JAN to 27MAR, based on out-bound departure date.... weekdays lower then weekends.... fares also vary depending on length of stay...

 

Just guessing, but I think Biergartens are usually open April - October but will close for bad weather. So take "reliably open" here to mean "should be open if the weather cooperates". I was in Munich this past April and ate/drank (HB Urbock) at the Chinesicher Turm. Highly recommended! The Fruhlingsfest was the following weekend, so if you go over some time mid-ish to late April you might hit it.

 

Well worth the purchase: Beer Drinker's Guide to Munich.

On my trip to Frühlingsfest some gardens were open, others weren't.

 

The Fruehlingsfest had indoor tents -- just like the Oktoberfest -- when I visited. Worth spending quite a bit of time there, IMO. That said, the Biergardens typically open from late April on, depending on weather.

 

But far fewer. I think there were only 2 when I visited.

 

And a noticeable (and pleasant!) lack of Italians, Aussies and Kiwis, I'll bet... ;-)

 

Wow, props to you, OP, for not asking where to buy Cantillion in München. ;-)

Also add drunk Americans and Brits, or so I've heard.

 

Not sure if this was coincidence or what but I ended up talking to Russians at two different tents at the O'Fest this year.

 

I was there and I was quite respectable, thank you.

 

Having lived in Munich for 2 years, it's pretty safe to say that most Biergarten will open up WEATHER PERMITTING. Great weather in March = beer sales. Might not have food available, but they will sell beer at the inkling of spring weather. Bad weather in JUNE? No Biergarten.

One other thing to consider if you are around: Starkbierfest (Paulaner Nockherberg) is from MAR 21 - MAR 30 2014. This is clearly the most "anti-tourism" fest going on in Munich.

 

Remember, if the gardens are closed, the cellars are open.
And yes, like some already wrote, the gardens will open at the first ray of Sun, whenever that may be.

 

When I was taking German classes at the Volkshochschule here, one of my classmates was American military, soon to be retiring and wanting to stay in Deutschland. He told a great story about how he happened across some beer fest in Munich and had a local guy at his table start getting on him about how Americans can't drink and so on. Well he didn't realize he was at the Starkbierfest and proceed to down liter after liter of I guess Salvator. Needless to say the story gets better/worse from there, but I just can't do it justice in writing.

 

We've all been there some time or another, haven't we ? It's part of the learning curve

 

The night before the opening of Frühlingsfest we went to Augustiner Keller for a couple. I asked the Oper if he had any Maibock. "No, but we have Starkbier…" Hindsight tells me that he was probably skeptical an American knew what he was talking about, tone of voice and looking up from a down-turned face, but my eyes lit up and I told him I'd certainly have a Starkbier… but please, only a half liter. Yeah, was afraid of a full liter of Starkbier… but I realized my mistake and ordered a second half liter.

 

"Weather permitting" is definitely something to keep in mind. We were there in May of 2009 and it rained intermittently the whole time. Augustiner Keller is well-covered so they would open at the drop of a hat, but the other places mostly stayed shuttered.