30 minutes south of Paso Robles is San Luis Obispo. You should definitely add it to your itinerary as a side trip or as you drive to or from Paso Robles. Here is what I found and recommend:
Apple Farm Restaurant: At 2015 Monterey St, this restaurant, right out of the 70s in terms of decor, is a good place for lunch. I had a very good Asian chicken salad before heading downtown to explore. Friends recommend the kitchy Madonna Inn where you can stay in themed rooms, eat and enjoy their bakery. The urinal in the men’s room is famous!!
The downtown area has some interesting restaurants, galleries and shops to explore. I really liked the cafes along the river and seeing the historic buildings.
Mission San Luis Obispo de Tolosa: Located in the center of downtown, this is one of the famous California Missions founded by Fr. Junipero Serra. The Mission in San Luis Obispo was founded in 1772 and restored fully in 1930s. The church is well-worth the visit.
San Luis Obispo Museum of Art: Located at 1010 Broad St., this is a small art museum that has exhibitions with a mix of painting, sculpture, fine craft, printmaking and photography in three galleries. Keep your eyes open for public art in the downtown area and throughout other parts of the city.