Another option: You know how the Start at area gives you a choice between Last Location, Home, or lets you type in your own region name? Why can't the grid selector work the same way -- choose from the 10 most popular grid, or type in your own grid's loginURI?
It wouldn't solve 100% of the problem, but it would cut out several steps for new users.Grid owners would then tell their users, type in your user name there, your password there, and this loginURL right there.