From the MVC:
The Methow Valley Climbers, a chapter of the Washington Climbers Coalition, respectfully asks visiting climbers to NOT camp or sleep in your vehicles anywhere along the paved section of Lost River Road or in the Fun Rock parking lot ... Please use a blue bag when on route and take all of your trash home. We thank you for taking responsibility during your visit to help keep climbers in good relations with the local community. Welcome to the valley and safe climbing.

From the USFS:
When planning your visit to the Methow Valley, please choose an appropriate campsite and use established toilets, or pack it out in areas without toilets. The roadside pullouts below the Goat Wall and Gate Creek are NOT considered sustainable places to camp due to proximity to the Methow River and lack of toilets.
Please see the uploaded map "Camping for Climbers" for campgrounds ($8-12 per night) and low-impact FREE dispersed areas with toilets within a few miles of your favorite crag. Free sites include: Goat Creek and Yellowjacket SnoParks (April-October only), and dispersed sites west of Monument Creek Trailhead.