Instruction:
Plan a 10-15 day trip from bay area to Arizona, Las Vegas, San Diego, Los Angeles

Response:
If you are starting from the Bay area you can follow the following circuit for a fun road trip:
- Day 1: Drive to LA. Rest for the night
- Day 2: Spend in LA - Visit Hollywood bowl overlook, LA county museum, Universal Studios, Beverly Hill
- Day 3:  Drive to San Diego. Spend time at Laguna Beach.
- Day 4: Across days 3 and 4 plan to explore Pt Lomas, La Jolla, downtown San Diego, hotel Coronado, Japanese Garden, and old town (only after 7 pm)
- Day 5: Drive to Joshua Tree.
- Day 6: Spend at Joshua Tree. Do short hikes across the park, and visit the cholla cactus garden, hidden valley loop, skull rock, and arch rock. End day at Keys views for sunset. If it is a new moon night, spend the night time stargazing.
- Day 7: Drive to Arizona. Visit Grand Canyon
- Day 8: Spend the day at Sedona
- Day 9: Drive from Grand Canyon to Page. Stay at Page for a night. Visit Lower Antelope Canyon, lake Powell. Visit Horse Shoe Bend
- Day 10: Drive from Page to Las Vegas. Check out the Vegas Strip and visit all the fancy hotels. End the day with a show such as Cirque De Soleil or any other show going on in Vegas.
- Day 11: Drive to Death Valley. Stop at all the points of interest such as  Mesquite Sand dunes, etc. Return back to Las Vegas for the night
- Day 12: Drive back home (bay area, CA)

You can always add Utah after Arizona (Zion national park, Canyonlands, arches national park etc.) to extend the trip further to 15 full days.