Are the showers only for people from that campground. We will be camping nearby at a site with no showers. Can we still use the facilities (for a fee, not expecting a freebie)

Yes for a $6 fee you can use the showers, refill your water jugs, dispose of trash, buy firewood, and use real toilets. Keep in mind that the showers are only open certain hours. I think it's 8am-8pm The best time for the showers is midday. No waiting usually.

The fee as posted at the gate was $6 per person.