The "correct" answer to that depends on a bunch of factors. What is your budget? What type of water do you fish. How good are your ramps on the waters you fish. Are the waters you wish to fish big enough that you encounter "Rough" water.
Your budget is one thing only you can answer. Here are some things to consider. If you intend to fish smaller bodies of water, launch on less improved ramps, or fish in stump infested waters then I would consider a tin boat in the 17.5 to 19 foot range. If you fish or want to fish larger bodies of water where the water can really get rough then fiberglass makes sense.
There are a bunch of nice tin boats to consider. Ranger, Tracker, Lowe, AlumaCraft, Crestliner, Express, Polar Kraft, and a bunch more make really nice tin boats. I have owned 11 boats in the last 40 years. If I fished mostly fast running rocky rivers I would want a mod v jon boat perhaps with a tiller outboard. If, like now, I fish mostly larger lakes I like a bigger aluminum bass boat. I have even owned a 20 foot fiberglass with a 200 hp outboard, but the cost got too high and I went back to aluminum. An 18 foot aluminum bass boat with a 75 to 115 can fit a lot of people's needs. Then, to make it a great fishing platform go with a 24 volt bow mount trolling motor, an onboard charger, and good modern electronics on both the front deck and at the console. This is a just a bit of what I would consider when you begin looking for your next craft.
Here is an example of a nice aluminum bass boat with a modern outboard (which is very important as many of your lakes in California are going to restrictions on outboard emissions). It has a very nice list of options and is obviously in good shape visually. The owner is asking almost $9000 and it is only 16.5 feet long http://santamaria.craigslist.org/boa/5782967882.html
Here is an example of what is available in fiberglass for the same kind of money. http://losangeles.craigslist.org/sfv/boa/5794833648.html
Obviously this would require better ramps to launch at. It would also require a much larger tow vehicle and will be much more expensive to operate and tow long distances. It will however give you the benefit of a better rough water ride and have much more storage, not to mention it will run a heck of alot faster.
Take your time and look around at a bunch of boats before you spend any money. By the way I do not want to make you think you need to spend $9000 to get a fishable boat, this is just an example of what is available in your area for the same amount of cash and yet how different your options were.
Take a look here at this final one for a lot less money ( I realize it is not close to you but is another example of what you could look for as an option. It is still in California so it is still priced in your market place. http://losangeles.craigslist.org/ant/boa/5788128639.html
Here is a couple of pics of my current boat. I bought it new and installed a small used outboard engine on it, due to my choice of fishing a small hp restricted lake. I moved over to the Chesapeake Bay ( here in MD.) so I replaced the used 25 hp outboard with a used 75 hp outboard. The boat is a very wide bodied Lowe Stinger 170. It has a ton of storage for tackle, rods, and boating supplies etc. It rides fairly smoothly except on the rough tidal waters. Once a year we visit some BIG Tennessee lakes and there the boat is terrific. It runs close to 33 mph has all the electronics I need and fishes just as well as my big fiberglass boat, but much cheaper to run. Here is a picture of my boat as it is now and one how it was with the smaller engine. I have both a regular front fishing seat and a longer post and butt seat and use both depending on if I want to sit or stand to fish. Most time I am standing and using the butt seat. I sit when I fish in rough water.
These are just a few things to think about, I hope I helped. I am going to share with you what i think is the best article I have ever read on the subject of buying a used boat. A friend, and one of the best anglers I have ever met, wrote it .At the time he was selling one Ranger boat and searching for his dream Range boat. This is not a two second read. As Bryan always says, get a glass of your favorite beverage, find a comfy chair and go for a ride with him. Realize upfront his favorite boats of all time are Rangers built back in the 90's, however all of his info is spot on no matter what you are looking to buy in a used rig. Please, let me know what you think after you read Brian's article. Everyone I have ever shared it with enjoyed it, but most came back with a few questions that pertained to their own search. Enjoy! http://www.baybass.com/node/200