The pca has, or at least used to have an alternative membership for those who dont yet have, but plan to have in the future, a Porsche. check the pcna website.
another option may be to become an "affiliate" member, all you have to do is get a regular member to add you. all members can add one person, its designed for a spouse, but there's nothing that says it cant be a friend to my knowledge.
And some pca regions will allow non pca members to drive in their events for a few bucks more than the regular members pay, this varies greatly depending on the local chapter.
For a higher steering wheel, extension adapters can be found, they also bring the wheel a bit closer. they'll work for some people.