The missing manual!
Anyway… The first thing you should know is that you're not the only one who couldn't fly into Boulder directly. Denver International Airport is the closest and only major airport associated with Boulder. It's only about 50 miles away from Boulder, so that's not too much of a hardship, especially since transit connections are so good (more on this in a bit).
The next thing you should know is that Denver International Airport (DIA) is not actually in Denver. DIA is slightly closer to Denver than it is to Boulder, but honestly not by that much. So if you were planning on taking advantage of your flight into "Denver" to site-see in the city… uh, that's probably not going to happen. In any event, while Denver is quite nice, Boulder is better in almost every detail except its lack of skyscrapers.
If you do want to site-see in Denver, it's very easy to get there from either DIA or Boulder. The A Line is a direct train from DIA to downtown Denver. Tickets are $9 and can be purchased with a credit card from vending machines on the platforms (to the right of the escalator) at the airport. That ticket also serves as a day pass on any RTD route, local or regional. So you can, for example, take the train to Denver, look around, and then head to Boulder all with the same ticket. The train leaves once every 15 minutes throughout most of the day, and once every 30 minutes if you're trying to take it at really weird hours (e.g. after midnight).
Speaking of Boulder… Getting between Denver and Boulder is by far most easily done via the FF1 and FF2 bus routes. These are express buses which travel between Denver Union Station (which has power, wifi, good food and nice couches, btw) and Downtown Boulder Station. Throughout most of the day, departures are once every 10-15 minutes. During rush hour (morning and evening), it's once every 3-5 minutes. The buses run effectively round the clock (if I recall, there's a 45 minute gap right around 3am), so you shouldn't have to worry too much about the schedule. The ride will take about an hour, and the ticket price is $4.50 (you want a "regional" ticket). Take the FF2 if you can; it skips more stops than the FF1 and saves about 10 minutes, but it only runs at rush hour.
Don't rent a car. Seriously. It'll just be a burden in Boulder unless you got a hotel that's way outside the city.
Take the AB bus from DIA. The bus takes the same tickets as the train ($9, vending machines on the platform) and picks up from the same place: the DIA Transit Center. There are several "A" buses, but only one "AB". Get on and ride all the way to the end (you can get off sooner if your hotel is somewhere along South Broadway, which includes areas near the venue). The ride will take about an hour and fifteen minutes.
The AB runs nearly round the clock on week days (there's a two and a half hour gap around 2am). If you miss the last one for some reason, you can always take the train to Denver and the FF1 to Boulder (as described above).
Do not take a taxi or an uber from the airport. It will be an $80-$100 ride to get you to Boulder even assuming optimal traffic.
WARNING!! For whatever reason, Google Maps does not understand the AB. I don't know why this is, but it's true. Don't trust the schedule on Google Maps for the AB. Use RTD's website instead. Google Maps works just fine for every other bus route, including everything in Boulder, just not the AB.
Three options in descending order of excellence:
- Bike
- Uber
- Bus
Uber is ubiquitous in Boulder (and in Denver). You will have no problem getting one when you need it. Biking is going to be faster than an Uber in almost all circumstances, and obviously it's much healthier and cheaper. :-) You can rent a bike at most bike shops (there are a ton all over Boulder), and Boulder has a municipal bike share program called "B-Cycle".
The bus is very convenient within Boulder, especially if you're going up and down Broadway (most of the city is stretched along that axis). Departures are frequent and reliable, and the service is used extensively by the locals. Fare is $2.40 and comes with a 2 hour transfer window (ask the driver for a transfer if you want one). You can buy tickets at the downtown transit center; you will need to purchase the "local" tickets. Day passes (like the one you used on the AB or A train) are also accepted on the local buses.
What should you pack? Good question.
I don't know. Boulder's Spring climate is extremely variable. It could be 30 degrees and rainy or 90 degrees and very sunny (Colorado sun is extremely warm). My best advice would be to check the forecast when you're packing your bags, preferably the night before you fly out. The forecast will not be definitive, even for just a few days in the future (I've seen it be wrong by 20-30 degrees Fahrenheit), but it will give you at least a decent idea.
So how would I pack for a visit to Boulder in late May? Aside from checking the forecast, I would probably pack some shorts, some pants, definitely some short-sleeved shirts, one or two light sweaters that I can wear over a short shirt, and a light jacket. I would bring an umbrella (not something you normally need in Colorado). If I was planning on going up into the mountains while in Colorado, I would also pack a winter coat (plan for literal Arctic conditions in the high mountains), gloves and probably a heavier sweater.
Don't drink a drop from Starbucks. Don't eat at a chain. Honestly, basically any random restaurant you walk into in Boulder is going to have better food than any of the chains that have locations in the city, and your options are quite numerous, especially downtown (near the mall). Trust Yelp and Foursquare. The only caveat is that Boulder restaurants do tend to be a bit pricier than in other cities, on average, but the quality is excellent.
Boulder has an extremely strong and diverse local coffee scene. Regardless of your taste in roast, there will be something local that appeals to you. The most important thing is to stick with a local roast. This is both due to the fact that the local cuisine is generally better, but also because brewing coffee at altitude is different than brewing coffee at sea level (owing mostly to the lower boiling point of water) and requires different roasting parameters. Local roasters know this and adjust, while national roasters (Starbucks, Peets, etc) do not.