I almost didn't attend Eric's party because the invitation seemed like a joke: a birthday celebration at a Starbucks at 5pm on a Saturday. Now that I've experienced it, however, I have trouble understanding why more 30-somethings don't throw their birthday parties at the coffee chain - it's like the grownup equivalent of McDonalds.
The employees seemed a little perplexed by the unannounced party, but they didn't attempt to kick out the few dozen of us that took over the Starbucks patio. It probably helped that attendees bought a good amount of coffee, plus various pastries to serve as the birthday cake. It also helped that though conversations were boisterous, they fell short of rowdy. That's not to say that the studying college students and LA duo working on a screenplay weren't put off by the sudden influx of people on their previously quiet area, but to their credit, they did subsequently join in singing "Happy Birthday" all the same.
I don't normally patronize Starbucks (because corporatism and caffeine, yuck) but I will gladly make birthday exceptions.