I cannot sign up to Lyft with an English number to use the Minnie Van?
You should try to signup to Lyft before you leave on your Disney World holiday. However, if you didn't, or you're getting a friend or family member to signup with your referral link to earn free credit, it's not the end of the world. Due to the way Lyft currently works, you have to enter an American phone number to create your account. This is no good if you're not American!
You cannot get past this stage without entering an American number, so either make one up, you find a valid one. We used Pop Century's phone number (which is 407-938-4000) and it let us create an account. You then go into your settings afterwards and change your phone number to your valid UK one (which it allows you to do). Hopefully Lyft will fix this in the future, but for now this is the only real workaround.