Regardless of whether you are using PayPal Express Checkout or Website Payments Standard, your customers do not need to register with PayPal before they make a purchase.
Website Payments Standard does not require that your customer have a PayPal account. Instead, when your customers check out, they will be directed to a page that allows them to log into their PayPal account or pay by credit card without having to sign up for a PayPal account.
PayPal Express Checkout does require a PayPal account, but this will automatically be created for the customer upon checkout.
Note: If you have never logged into PayPal before on your computer, your checkout box will look like this:
Note: If you have logged into PayPal before on your computer, a cookie will be set on the system, and your checkout box will look this. You will most likely see this screen when you test your payment process because you have logged into PayPal. To verify that your new, non-PayPal users will see the correct screen, you can delete your PayPal cookies or test in a different browser that you do not use to access PayPal.