undecided or agnostic.
The latter is almost exclusively used to refer to religious beliefs.
I'm not sure how you can "subscribe" to the side of a fence, though. I'd consider changing the wording!
verb (used with object)
1.to pledge, as by signing an agreement, to give or pay (a sum of money) as a contribution, gift, or investment: He subscribed $6,000 for the new church.
2.to give or pay in fulfillment of such a pledge.
3.to append one's signature or mark to (a document), as in approval or attestation of its contents.
4.to attest by or as by signing.
5.to append, as one's signature, at the bottom of a document or the like; sign.
6.to agree or assent to.
This is the context in which I was using the word "subscribe"