Last note about the water was a couple months ago. Had the giardia in the water been resolved?

Caution signs are still up

Signs are just a precaution. Giardia can be found in any natural body of water. Your dog is just at risk in any lake river or stream anywhere.

Your dog can get giardia from any natural public water, which is what the water in the park is. Caution signs legally have to be up, but there is no more risk at the park, than there is letting your dog be in a stream in the mountains.

I wouldn't trust it. People will always let their dogs potty in the water and thats how Giardia happens