Traveling on a budget in CA- book hotels in advance or last minute?

Like Spencer mentioned September is prime time in LA - I'd book in advance and don't forget about Airbnb! There's also a great little hostel in a prime location in West Hollywood called Banana Bungalow West Hollywood Hostel you should check out if you're trying to stay on a tight budget.

Air BnB works really well in the cities. Also, don't forget about Hoteltonight.com - It's a great place to find same day or next day hotels at a really cheap rate. You can stay in a really nice hotel for sometimes 1/2 the price of a regular room rate if you use them. 

Also, there are a lot of small towns along route 1 up the coast, so I doubt you'll have any problems finding a place to stay. As lot of them are small hotels/motels that expect last-minute through traffic! 

I think that you should consider direct booking. Skip the agencies, this time of year in California. You can arrange a good hotel (maybe even a great deal) last minute in so many places along route 1. I think people fail to realize that there's still a road-trip, whimsical feeling upheld along Pacific Coast Highway. Businesses actually expect walk-ins, thru-traffic and last minute guests because so many towns sit right off the side of the road.

You just need to know your handful of stops and make sure and check the dates for what's going on there. (for example, don't show up in San Diego during Comic-Con in July- or any other place that hosts a big event) If it's clear to you, the stops along the way, start looking directly on hotel websites and make a phone call or two for great rates. I think this is starting be be a little old school- but I also think there's a lot of value in doing it this way! 

I just got back from Santa Monica this last weekend- so many good vegan,eats and treats and I'm not even a vegan. I recommend CarmelEspecially if you like wine. Check out the secret-garden hotel: http://www.laplayahotel.com/rooms/garden-patio/ maybe you'll get lucky. In Laguna Beach maybe look into a reasonable, beach hotel there:  http://www.thelagunabeachhouse.com/

My friend told me about this app called HotelTonight for last minute hotel deals - discounted prices for super nice hotels. Worth checking out!

I'd go ahead and book your accommodations ASAP. September/October is really like California's summer from L.A. to San Francisco. It's in my opinion the best weather and the best time to visit a lot of the places you're going, so hotel prices are going to be high. As someone else recommended, there are a series of hostels (and some pretty cool ones) dotting the coast, such as at Pigeon Point Lighthouse, Hostel Santa Cruz Hostel Society, HI - Monterey. My pick would be tapping into HomeAway and Airbnb. Also, you may find some great tented campgrounds and cabins, such as Big Basin State Park, and a number of other parks and campgrounds. All of these recommendations book up quick.

Do you like Youth Hostels?  They are pretty reasonable, but I'd recommend advance reservations.  You can drive from Santa Monica to San Francisco in one day, but its a long drive & I'd recommend breaking up the trip with an overnight somewhere in between.  The HI - San Francisco: Fisherman's Wharf is very nice & well located, but again, advance reservations!  If you don't like youth hostels, I'd research motels along the way & get reservations in your price bracket.  I wouldn't leave finding hotels in that area to chance (and prices never go down...)