I am planning an approximately 17-day tour in California. The current plan as it is includes:
A four-day car-ride from crescent in the north to San Francisco, a week in San Francisco, one day car ride to Los Angeles, five days in LA and finally, one day trip to San Diego.
The trip is planned for October.
I will really appreciate some advice regarding places to see and ways to cut down expenses.
Any other recommendations will be welcomed.

There are others here who can give you much better specific information, so I will start the discussion with one tidbit...give yourself at least 3 days to drive from San Fransisco to LA. This area deserves much more attention that it can get if it justs flies by your automobile window. Buy a cheap cooler & fill it with soft drinks & water, maybe a few snacks, and stop along the way at the wonderful overlooks to picnic & just enjoy the view. Don't miss Carmel and the Monteray Peninsula, the 17 mile drive, Hearst Castle...too many sights along this trail to mention in this post. Others have asked questions specifically about this drive. Please reference them as you plan this part of your trip.

Much as we love SF, I am going to suggest that you cut your stay in SF shorter so you can have more time to drive down to LA. We live here and the last time it took us 4 days to drive to San Diego!! Can't resist stopping! See Carmel, the 17 mile drive, Big Sur (check to make sure Hwy 1 is open), Cambria and Hearst Castle (make reservations ahead from your home for tour #1 if you've never been there), Solvang and some of the missions--La Purissmima or Santa Inez--Santa Barbara then L.A. You can see LA in a few days, assuming you aren't going to Disneyland or Universal Studios, both of which take one day minimum, then San Diego which should be given 2-3 days at least. It's a very big state with so much to see. There's a book called "22 days in California"--try to find it, but I think they are even unrealistic with their itinerary. You realize you are leaving out Tahoe, Yosemite and Palm Springs---most people choose to do either southern or northern California with the "border" being Hearst Castle at Cambria. Good luck.
PS While driving, if you see an "In and Out Burger" drive through, stop---they are really good burgers--not anything like McD's.

Unless you call crescent city home...there is a lot to see there im told....take your time driving....dont stay too long in one place and then not be able to stop when ever the mood strikes you....there are so many things to see..

I agree with cutting down the city stays and lengthening the travel times. Humbolt Redwoods is an attractive park. Muir Woods just north of SF is lovely. We usually find 2 days in SF enough, with cable car rides, Chinatown, Golden Gate Bridge, etc. The tidepools at low tide at Moss Beach are great. Point Lobos State Park and drive to Big Sur always dramatic. If there is a recent edition of Hidden Coast of California, it was a good source for out of the way places and restaurants to keep the prices down. We also hit the cities on the weekends for much lower accommodations prices.