As Mark correctly states -
you CERTAINLY CAN use either a Credit Card - or even an Electronic Check with PayPal.
That the PGCA does not have a "merchant account" other than PayPal certainly does
not preclude the use of your Credit Card (or even drawing funds out of your Checking account) for Membership using that same "PayPal" link for Memberships...
And -
No - you do
NOT need to have a an existing PayPal account to use either as a "PayPal Guest"...
Best to all..!
John