Here are some answers and clarifications for you! First, if you purchase the game from https://buy.guildwars2.com/ you'll automatically be sorted into the right region.
And don't worry -- we want you to play with your friends wherever you are. This policy only affects where you can login from -- not which worlds you can access. People from NA will be able to play with people from EU at launch. We've got two datacenters -- one in NA and one in EU. Those who do not fall into either of those two regions will default to the NA datacenter.
Finally, we are aware that a lot of our players travel, and we are looking into a solution for you.
502 - Web server received an invalid response while acting as a gateway or proxy server.There is a problem with the page you are looking for, and it cannot be displayed. When the Web server (while acting as a gateway or proxy) contacted the upstream content server, it received an invalid response from the content server.
Getting a 502 error? We've got more information on that from Mike O'Brien:
"We're working on this error now. Since you're seeing this error during the registration phase, you've already successfully purchased the game, and have a key you can use to complete registration any time. There's no need to stay up tonight waiting. " ~RB2