Ask HN: How do you check internet speeds for offsites?

Just started our annual tech offsite with a team of roughly 20 people and the inevitable thing has happened: we're sitting together, supposed to code away and 3/4 of the people are blocked as they can not download critical resources to advance on their projects.

What's your experience with checking internet speeds when planning tech offsites? Any good tips on how to avoid such a situation the next time?